This is a relatively simple project which should be done at least once a year. Brake fluid absorbs moisture easily and not changing it regularly can lead to internal corrosion of your brake parts. CAUTION: ALWAYS WEAR EYE PROTECTION WHEN WORKING WITH BRAKE FLUID! FAILURE TO DO SO COULD CAUSE BLINDNESS IF YOU GET IT IN YOUR EYES!!!

It helps to have two people to do this, but it is possible to do it alone if you are very dextrous.

To bleed the brakes you first put fluid in the reservoir, then pump the pedal/lever about 10 times.
Hold the lever in or the pedal down which ever your working with and then open the bleeder which is located on the caliper (probably need two people), watch out for fluid and air coming out (it hurts when it gets in your eyes).
After the initial burst of fluid/air out of the bleeder, quickly close it BEFORE you let off the pedal/lever Now pump the pedal/lever until it starts to get firm again.
If you're just bleeding the brakes repeat until nothing but fluid comes out of the bleeder.
If you're purging the old fluid repeat until fluid is clear (your old fluid is probably dark brown) or at least 10x to make sure you get all the old stuff out.
Keep pumping the pedal/lever and holding it down/in and opening the bleeder until you get brakes.

WARNINGS:
 

• YOU MUST KEEP THE RESERVOiR FULL OF FLUID, NEVER LET IT GET LOW.
• NEVER LET THE PEDAL/LEVER UP or OUT WITH THE BLEEDER OPEN, IT WILL JUST SUCK AIR INTO THE SYSTEM.
• Brake fluid eats paint, so it is best to lay rags down or if some spills on anything wipe it off right away.