You will need a hammer and small and large diameter punch. On the new hinge, you will see the 4 pins sticking out of the base of the hinge. The small punch diameter needs to be a little smaller than those pins. pic: http://bit.ly/door_hinge
1. Locate the 4 pins on the broken hinge, drive those pins out with the small punch. Just drive them straight into the hinge, they will fall out the back, then the old hinge will come off the body.
2. Install the new hinge. (Do not install the Door to the hinge)
3. Use a punch that is slightly larger than the pin diameter and drive the new pins into the hinge, seating them flush with the hinge base. Do this in one quick blow, otherwise the pins can fold over and break.
4. Install the door to the hinge and engage the door spring.
Hope this helps, it's hard to describe some of the little details, but you should be able to figure it out.