While an increasing number of people use Facebook to keep in touch, not everyone is on board yet. If you want to send an invitation to someone to join the social networking site, add him to the address book associated with your e-mail account. Ask Facebook to find the friends in your address book on Facebook, and you are able to invite the friends who don't currently have an account.
Log in to your Facebook account and go to the home page. Click the "Friends" link, located near the top of the screen in the left column.
Click on the "Find Friends" link next to your e-mail service provider from the list, or choose "Find Friends" next to "Other Email Service" if your provider is not listed.
Enter your e-mail address and the password associated with your e-mail account when prompted. Click the blue "Find Friends" button.
Leave a check mark next to each friend from your e-mail address book that you want to invite to Facebook. Uncheck the box next to a friend if you don't want to send him an invitation.
Click the "Send Invites" button just beneath the list of your address book contacts to complete the process.