When I started on my journey, the first place I started from was with The Creative Penn. Make sure you sign up for here newsletter.
Also, take a look at this KDP Tools and Resources list. They cover the most general use cases. I use Sigil to create my ebooks in the ePub format and then use Kindle Previewer to know how it will look on a Kindle device as well as create a file that I can upload to the Amazon store.
Have a great weekend.