How do I add the .kfx version of my book to my Windows Desktop Kindle app?

Hi!

There are two ways to do it:

1. Move the kfx file to the content folder of the Kindle reader and restart the app. By default, it is "C:\Users\%Username%\Documents\My Kindle Content". This directory can be changed in the Kindle app settings (Tools > Options > Content).

2. If you associate kfx files with the Kindle app, simply opening the file will also work. To do this, right-click the kfx file, select "Properties" from the context menu. Then, in the "Open with" field, pick the Kindle executable (it's usually located at "C:\Users\%Username%\AppData\Local\Amazon\Kindle\application").

Please let me know if you have any further questions.