There are pros and cons to publishing with Amazon, but if you've definitely decided you want to self publish your book and have it publicly on sale, I think it's the easiest and most effective place to start.
Some of the advantages are –
You don't need to qualify or be accepted, and there's very little waiting time. It's entirely possible for you to start the process now and have a complete stranger reading your book the following week.
There are no up front publishing costs. Amazon take their cut of each sale before passing the remainder on to you.
You are entirely in control of all decisions such as book content, editing, cover design, title, pricing etc etc.
The process isn't particularly difficult – and there are lots of online resources showing you exactly what to do.
The author is free to choose their own editor, proofreader, formatter, cover designer etc etc, or opt to do some or all of these things themselves.
Any royalties due are paid monthly (a couple of months in arrears) and you can check frequently to see
what you've earned.
You can see your sales figures promptly and as frequently as you wish.
You may publish an ebook (kindle) version, a paperback, or both.
Copyright remains with you.
If you wish to make a change to the book (because you've become aware of a typo for example) you can do so quickly, easily and at no cost.
You can buy 'author copies' at a cheaper rate to sell in person.
Amazon are probably the largest book retailer, so you have the potential to reach a huge worldwide audience.
Some of the disadvantages are –
There is almost no quality control. You may get alerted to some typos or the fact that you've spelled your own name incorrectly on the cover, but most errors will go through unchecked. If you accidentally upload only the first seven chapters not the whole book, that's what will be published. If you upload a story with huge plot holes or grammar so bad it's almost unreadable, that's what will be published.
You will be completely on your own. Unless you pay for help or can get support from a writing group or knowledgeable friends you will have to make every decision yourself and undertake every part of the process yourself. This includes marketing. You may have had adverts from Amazon suggesting you buy a particular book – they usually only do this for books which are already selling well, or if people have chosen to 'follow' you. They won't do that until they've heard of you.
Bookshops very rarely buy from Amazon. That's because they'd have to pay the full cover price and therefore can't make any money. (Some will buy from you directly, if you ask nicely, are a local author and a regular customer.)
Libraries very rarely buy from Amazon. It's easier and cheaper for them (and bookshops) to buy through book distributers – and these companies will be able to supply all the best selling and most frequently requested books.
If you decide to go ahead, here's a quick checklist of what to do...
1. Write a book.
Rewrite it, edit it, get feedback, rewrite it, edit it etc etc until it's as good as you can possibly make it. A professional editor, and / or experienced and reliable beta readers are advised.
Get the book proofread. I strongly advise NOT doing this yourself.
Buy or create a cover image. That's just a front cover for ebooks. With paperbacks you can create the front back and spine and upload as one pdf, or just upload the front cover image and use Amazon's cover creator to sort out the rest.
2. Choose whether the book will be ebook or paperback and format accordingly. If both you will need two files as ebooks don't have page numbers and headers and footers. Amazon provide templates you can use which will take care of things such as the correct page size and margins. Ebooks can be uploaded as a Word doc. For paperbacks you'll need to convert it into a pdf – you can usually do that easily using 'save as' or by selecting the pdf icon in your toolbar.

3. Create an Amazon author account. They might want to check you're really you, and you might have to complete tax forms. You'll need to give your bank details so they can pay you. This can take a while, so maybe do that in advance. You won't be committed to publishing with them if you change your mind.
4. Follow the step by step instructions for uploading your book. You can either use their free ISBN or provide your own. You'll be asked for a description – that's your blurb or sales pitch. Keywords are the words people might type in when searching for books like yours. Categories are the genre (or genres) which best describe your book.
5. Once the text and cover are uploaded you can preview the book online. I strongly recommend you do that carefully, even if you intend to buy physical proofs as it will be quicker to make changes at this stage and spotting mistakes now will save you money on further proof copies after you've made corrections.
You will then have the option to buy one or more physical proofs before you publish the book. Although that will cause a delay it's probably a good idea to see what your finished book looks like before you put it on sale.
6. Next you say where you want the book to be on sale, how much you want to charge and what percentage of royalties you want. There will be a price range to select from and there's an option to get a suggested price guide.
For ebooks you can choose 'KDP select enrolment'. If you do that, readers who subscribe to kindle unlimited can 'borrow' your book and you'll receive a small payment for each page they read. You can only do this if your ebook is available exclusively with Amazon. You enrol for three months at a time, with the option to automatically renew. You can take your book out and publish it other places later if you wish.
7. Press the button to publish your book.
8. Sit back and wait for the money to roll in – or do some marketing to give yourself a chance of that happening.
In case you're wondering ... All my books are available through Amazon. Some of my novels are also published through Ingram Spark (all my new books will be published with them and my entire back list will be added over time). My ebooks are currently available exclusively through Amazon and are enrolled in KDP select (meaning that if you subscribe to kindle unlimited, or sign up for a free trial, you can read them for free.)
If you have any questions feel free to ask. I can't guarantee I'll be able to give a sensible answer, but it's possible!
If you found this post useful or interesting please say so in the comments, as that will encourage me to make further posts on things such as publishing with Ingram Spark, book marketing, creating audio books ...