how do I get rear brake cylinder to go in?

What do you mean brake won't go in???? Explain that and I might have an answer.

To insert the rear brake pads, you need to use a special tool (OEM/Rear disc brake cube for use with 3/8 in. drive tool) to push the caliper brake cylinder down. The tool costs about 12 dollars and attaches to your 3/8in socket driver. You will need to use a small extension. You have to push down on the brake cylinder while turning with the cube tool counter clockwise for one brake side of the vehicle and clockwise for the other side. Sorry, I forget which side is counter and which side is counter clockwise.