Open Adobe Digital Editions.
Select Library > Authorize Computer...
The 'Authorize Computer' dialog box is displayed.
Under 'eBook Options', enter your Adobe ID (email address) and password.
Click 'Finish' to close the 'Setup Assistant' dialog box.
thanks for this, it was so simple, I needed a new email and password because I had already used this one for a different computer, but the library books transferred like a breeze after I authorized my computer to receive them.