Welcome to MR (MobileRead), gillian107.
This is a great place to ask for help and find information. Have you discovered the sticky threads at the top of the Sony forum? There is a great informational one called "
Sony Reader Info, Start-Up & Reset Guide" that links to the
MR wiki. It has a section all about borrowing books for your reader (
Borrowing library books).
You can also read about
ADE (Adobe Digital Editions),
acsm,
DRM (Digital Rights Management), and different
E-book formats in the wiki.
Have fun exploring and just ask if you have any questions.