download redsnow
hit jailbreak
tadaaa
more specifically:
follow this guide(i just googled it)
http://absinthejailbreak.com/jailbre...-on-mac-5-1-1/
after jailbreaking, you should have cydia installed. Go to cydia and search for ultrasnow. Ultrasnow will let you unlock your phone. Make sure you have your tmobile chip in there and everything should be ok.