There are several ways to find people on MySpace who might be in your target audience--by searching for murder mysteries, historical romance, _ self-improvement_, organic food, or whatever field you're in. Perhaps there's a famous writer whose style you emulate, and you'd like to find other admirers. Once you've found potential friends, you can send a request for them to "add" you as a friend. The invitee can accept, decline, or ignore your request, although most people accept.
Once you're friends with someone on MySpace, you can post comments on each other's profile pages and see each other's full circle of friends. Here's how to find friends and potential readership on MySpace: