could someone tell me how to compress rear disk brake cylinder

 

You probably mean the rear caliper piston....

You need a special tool that you can get at any parts store. It looks like a cube with alot of ***** on it. Theres a different pattern on each face of the cube. Find the face where the ***** will fall into the caliper piston, use a rachet to screw the piston back into place.

 

needle nose pliars will work too. At least what chiltons states.

Proph

 

turn them clockwise..

 

I used a large C-camp and a piece of wood.

 

That only works on the Front brake pistons... The REAR ones need to be TURNED IN as state up above.