You can connect your Go Vocab account to Facebook to compete against your Facebook friends on Go Vocab, and also so that you can use your Facebook profile picture as your Go Vocab icon.
You can do this by:
Signing up with Facebook
Or if you have already signed up, you can go to the settings page and click 'connect to Facebook'
If you are unable to connect to Facebook it may be that Facebook is blocked on your school network - in this case please try again at home