If you don't have the right tools....then:
1. remove fork
2. place fork in passenger seat of automobile
3. drive to LBS
4. pay 10 bucks to have it cut properly

dude, if you mess it up, then you are out a fork and big bucks if you've never done it before. And if you never seen a fork alignment cutting tool...I would take it to the LBS.

The bike shop I got mine from cut it in about 90 seconds for free.