[wallcraft]

If you select an ebook in Calibre it should show Formats: EPUB, MOBI

Connect you Fire via USB to your computer. On the Fire you should get a "Transfer Files" screen. Under Windows you may have to select "use File Explorer" or something, and then it shows up as a KINDLE drive (in my case it is drive D). At the same time in Calibre you should get a new Device icon and there is a new "On Device" column. Select any ebook, or select a range of ebooks (left click on the first and shift left click on the last ebook to select all between the two). Then right click and select Send to Device -> Send to Main Memory. You get a job and a spinning progress wheel, and when the job ends the ebooks will be on your Fire (actually in Documents) and they will show up in Calibre in the "On Device" column. Select the arrow next to the Device icon in Calibre and select "Eject". I then also tap the Disconect buttom on the Fire (since the eject does not show up automatically, as it does on my Kindle 3).

If this does not work for you, be more specific about what fails.

By the way, if you don't have a MOBI version of the ebooks Calibre will ask you if you want to make them when you choose Send to Device -> Send to Main Memory.

You need Calibre version 0.8.27 or later.

EDIT: the ebooks might be under the Docs tab on the Home page, rather than the Books tab. As osnova implied, you can also look in the Documents folder while it is connected via USB to see if the files are there.