To link your Facebook or Twitter profile to your TimesFree account, go to the "Settings" page. Just tap to link either account - please you can only link to the account you're signed into with iOS.
Once you've linked your accounts, other members of your groups will be able to connect with you using social media. Don't worry - only people in groups you've joined will see this information.
If you created your account using an email address and password, you should continue to use these details to log in to TimesFree.