By "main site" WanderingAries means
CoHTitan.com. Login there with your Titan Account Details and then you can Link up your CIT and CGT Accounts by entering in the Site Logins in each designated field.
If you also have an Account for Faces, the Planner and/or Red Tomax, we have an issue in the Titan Interface with those at this time, so if you have an account on any of those, you'll have to link them up at a later date.