You can now download your free books from these links:
Right click the mobi or epub and then click ‘save as’
Click the download link then choose “Open in Kindle” or “Open in iBooks.”
(On some models of iPhones and iPads, you have to click download twice)
Right click the chosen file and then click ‘save as’
You may need to use the Kindle transfer app to download the file to your computer and then send it to your app.
You can follow the instructions here if you’re struggling: