Check out this cycling video tutorial to see how to do the bunny hop trick on a bicycle. Your BMX instructor for the day goes through the very basic steps with demonstrations on the bike bunny hop, along with some out-takes at the end to ease the pain of falling on your ass.
The bunny hop move is wear the whole back wheel leaves the ground. That's it. It's without assistance of any ramps or anything, it's just pure muscles in the arms and back, and scooping action the legs and feet. So make sure you're wearing the right shoes, and the proper safety gear. Then go out and see if you can do the bunny hop bicycle trick yourself.