It is the same method as for adding a regular attire. But as Jericho already has a second attire, it is a little simpler.
Just change 11 and 12 instead of 01 and 02.
But you will need some kind of cheat device to make it accessable in the game. All second attires are locked by default, and their is no in-game code to unlock it, like for Cena, Orton and Santino.