Ya setting it up properly is a bit complex for new rails programmers.
Here's another really good source: http://blog.hasmanythrough.com/articles/2006/04/21/self-referential-through. Scroll down to see a "friends" example in the user comments.
Basically you've got a user table (nodes) and are connecting users inside that table with each other through "friendships" (edges).
Cheers, Chad