1998 BMW M3 changing rear brake pads

Remove wheels, pry the anti rattle clips from the calipers and then locate black plastic plugs at rear of caliper area and pop them off, exposing caliper locating pins. With a 7mm Allen wrench, remove caliper pins, push brake piston back into caliper with channel lock pliers, clean contact points and apply anti-seize compound, install new pads and reassemble in reverse order. Now having said all that, I strongly recommend you consider seeking professional assisstance in accomplishing the task as the job may seem simple, but there is tremendous liability involved in performing brake repairs. You may also consider purchasing a repair manual for your vehicle, I recommend Bentley publications.