What button to access the police computer on gta iv?

First, you find either a policecar, police truck (enforcer) or an FIB Buffalo. Then you must park and press LB for Xbox, or L1 for PS3, and the police computer will come up. If you feel like doing a police mission, select 'VIEW MOST WANTED', and choose any person you like. Make sure you have a weapon (preferably a gun), and a blip will come up on your radar. Go to it, and you will have to eliminate enemies in a gang.