Need step-by-step for abs pump install

There is no pressure the pump just comes on and then turns off. Then the ABS light comes on the dash and stays on. I have had the codes scanned on it at a shop, and they said the accumulator is leaking. But it could also be the abs pump. They also made a note that the brake booster for the normal brake system was leaking some brake fluid. I purchased a used, tested and functioning abs pump from online and need help installing this. Any help will be greatly appreciated in this situation.