To read ebooks borrowed from your library, you must authorize your PC with Adobe Digital Editions by entering your Adobe ID.
Open the Adobe Digital Editions application on your PC. You can access your applications from the Start menu by clicking the Windows icon on your computer's taskbar.
Click Help on the menu.
Click Allow Computer...
Enter the email address and password used in Step 1. Create An Adobe ID.
Click Allow.
Adobe Digital Editions can now be used to read ebooks borrowed from your library. You will no longer need to repeat the previous steps.