dude, seriously. you need a new one.
don't try to just flush it out. it won't work.
get a new one, along with the rest of the system.

but to answer your question, it isn't hard, Just do the same process you would like you were bleeding your brakes after a brake job. Start at the passenger side rear. pump the brake pedal a few times. then hold the brake pedal down. loosen the bleeder enough to let the fluid/air come out, then tighten quickly. before letting off the brake pedal. then repeat until the fluid comes out clean, clear, and bubble-less. then move to the next caliper...