I uploaded a kid book.
The book was short with a lot of pictures using MS Paint.
I used 1.5 spacing for the text.
I used Word 2003 and saved as .doc.
Use page breaks to separate text and pictures into pages. In Word 2003, it is insert, break, page break.
You can put your cover in the book file. The product page cover has to be a certain size.
For Word, you have to have the pictures in .PNG. I used MS Paint to save the pictures in .PNG. For the product cover, I used .JPG.
This is the easiest place to do an ebook.