I have a Kindle Paperwhite and a Kindle Fire. I'm trying to get both devices combined in the same account.
If you got to the Amazon Kindle website (using a laptop or desktop is better because of the typing involved) and log in and re-register both devices to the same email and password they will automatically show up as two devices on your one Kindle account and you should be able to use them to share the books on your cloud. The way I understand it is if you have two different user ID's and passwords, you will have two different clouds.
×