To pick a Career Mode Char in Versus Mode, go to the character select screen and press L1 or R1
Use the career mode and collect the indicated amoount of DNA points:
Get Long: 5,000 DNA points
Get Shina: 10,000 DNA points
Get Kohryu: 30,000 DNA points
Get Uranus Character: 50,000 DNA points
Get Dragon Ryoho: 100,000 DNA points