I just published my first book on Amazon.com this month. I'm no expert but here are the cliffs:
You basically have two publisher options: Lulu or Createspace
I've tried both and CreateSpace is better. Books are about $5 per copy on Createspace and $10 per copy on Lulu. Quality is also better with Createspace IMO.
Most common size is 6" x 9" which I would recommend.
You can submit a word doc or PDF for the actual content of the book. (I did a PDF I created with Adobe InDesign).
You submit a single file PDF for your cover (front, back and spine).
Ownership of the book depends. If you want full ownership you will need to buy an ISBN from Bowker:
https://www.myidentifiers.com/ for $125.
They say you need a unique ISBN for each book version (Paperback, Kindle, etc, etc) but I don't think you necessarily do.
If you don't want to provide your own ISBN you can have Lulu or Createspace provide it for free where they own certain rights.
When you publish with Createspace it will automatically post it on Amazon.com
You can also get your book on the Kindle easily through Createspace as well.
My end result:
Rule By Ignorance: Quinton Figueroa: 9780988342712: Amazon.com: Books
There's still more to it, but that's the cliffs of my experience.