How to add devices to my ADE account?

Hi there,

I have an old Nook Color from Barnes & Noble and used to transfer ebooks to this device. However, I bought 2 new Nooks HD but when I connect them to the computer, the ADE software does not recognize them (they don´t appear on the right side of the screen like the Nook Color does) so I am unable to transfer the ebooks. Question: how can I add devices to my ADE account in order to transfer ebooks from now on? Looking forward to hearing from you.