2. If you have played two previous Assassin's Creed games, you unlock Ezio.
3. If you have played three previous Assassin's Creed games, you unlock Connor.
If there is no record of previous game ownership for you, you will not be able to unlock these costumes. However, every time the game launches it performs this check, so if you go and play the previous games listed below for a little while you'll be able to unlock them.
Assassin's Creed Revelations
Assassin's Creed III
On the Xbox One and PlayStation 4, as long as you log in with the Xbox Gamertag or PSN ID you used on the Xbox 360 or PlayStation 3, this information should carry over without any issues.
Note: It can take up to 24 hours for the tracking systems to update fully.