Eggs can be found laying around town, can be picked up off the body of a downed prep who was throwing them at you, can be purchased at Yum-Yum Market, and can also eventually be found on your bedroom floor. Once you get the eggs head into town and throw the eggs at the cars. Press to get to the eggs, to throw them. It can not be the same car. A carton of eggs holds 12 eggs, so you must have at least 3 cartons.
An easy way to hit cars is to press to go into aiming mode.
**You can check how many cars you have egged:**
Start---> Stats---> General---> Vandalism---> Cars Egged or