"You were there yesterday."
Translation:Ty jsi tam včera byla.
No, that's not correct. The enclitic -s has to be 'the second unit of meaning.' If you don't know what that is, I suggest you check the tips and notes and/or one of the recommended resources.
If you want to use the personal pronoun (which is not necessary), the enclitic -s is added to the personal pronoun, that way it's in the 'second position': Tys tam byl včera.
Compare it with Byls tam včera. It's also in the second position here.