On paid plans you can have as many Overdrive sites as you need, the licencing is per user not per site. 

To add a new site, simply click on the + Add new site button.

For Shared Drives see also Google Shared Drives.

If you need help or have any questions on setting up a new site please contact us, or for instant help click the Chat tab at the bottom of the screen.

Note: There is a bug in Internet Explorer that sometimes stops the selection of Drive Folders in initial site setup. If this happens to you we recommend using Google Chome or Firefox to add a new Overdrive site. Alternatively you can set up an Overdrive site from within Google Drive. Navigate to the folder you wish to use and choose Open With - if you dont see Overdrive as a choice, go to Connect more apps and search for Overdrive. Once added you will be able to create a new site from any Drive folder.