Kindle App on iPod

[Paddypix]

I have lots of ebooks bought from Amazon, all of which appear in my Kindle apps on iPod and Android phone, but I also have a lot of non-Amazon books which don't show in the apps although it's easy for me to drag and drop them into my Kindle Paperwhite. I can't find a way to get them onto my iPod Kindle app. Any help would be much appreciated as always.

Edited to say that I have discovered a way of getting my ebooks onto to iPod by using the Books app rather than the Kindle one. I had to convert them from mobi to epub.