here's a link to the form:
http://www.dmv.ca.gov/forms/reg/reg230.pdf
fill it out, mail it to the address on the form, send in your 19 bucks, and wait. (your local DMV is clueless and can't handle it. at least, costa mesa couldn't. and they don't have the plates there anyway, so you still have to wait.)
as for the next question you're about to ask, use your bicycle's serial number for the VIN, and for the engine number, i use the same serial number, except i put an "E" in front of it. ("E" is for "engine," get it?)
I also engrave that number onto the engine itself, because when you register your bike, it goes into a database, and if it gets stolen, it can be tracked. it's also a lot easier to show the cop the engine then it is to flip over my bike so he can read the serial number on the bottom bracket.