Stolen phone how to use find my iphone?

My brother phone was taken right out of his front pocket by a pick-pocketer
his new iphone 5 is gone!
how do i track his phone using find my iphone on my phone?
i don't think he has find my iphone set up on his phone so please help its really important

You do not have to have Find My iPhone set up on the phone. Go to www.icloud.com and input his Apple ID and Password to his iphone and click on Find My iPhone. It will track it from there. Its pretty accurate as well.