I put my manuscript in the Vellum software and it generated an ebook for me--Vellum is noted for nice ebooks, but there are other apps that are cheaper. Just google it. Then you can either hire someone to make you a cover on fiver.com or go over to Etsy.com or creativefabrica.com and buy a ready-made, editable cover. You upload it all to Amazon, with keywords, description, etc. You decide what formats and selling price you want to use and hit publish. You can find plenty of YouTube videos and free kindle books on Amazon to walk you through the process. They've made it pretty straight forward once you stick your toe in the water. They'll give you a number, equivalent to an ISBN or you can go buy your own. That's what I did because I've got ambitions to publish more books and frankly I've sold quite a few books in other markets besides Amazon--you can't do that if you use Amazon's number. But if you've got your own ISBN (which you obtain from Bowker) you can sell your work anywhere.
I think you can find a good starting place at kdp.amazon.com. If not just google KDP books.
Everything you need to learn to get the job done is available for little or no money online. Good luck to you and enjoy the learning journey!
= new reply since forum marked as read