Hi
mrpocketpossum is really helpful with his advice.
Most caliper's have a bleed nipple on them, Have a look and see if you can locate it, it might be covered by a rubber dust cap. Slacken the nipple off and gentle push the piston in, use a cloth to soak up the brake fluid that will come out the nipple, once you've pushed the piston back retighten the nipple. Do the other side the same then top up your brake fluid.
paul, May 2008