Hi, fist use vacuum pump with reservoir to empty master so it will not leak onto the paint and other components. Use old cloth under it to collect oil that can not be removed.brake loose brake lines using pipe wrench. Remove two attaching nuts and pull it out.
New unit- fill new muster with Dot-4 brake fluid. IF it comes with fitting and clear plastic tubes attach them to ports and feed tubes to master filler neck. place master on Vise and secure it in position same as it installed in the vehicle. use large screwdriver to push piston and bleed all the air out of it. As you push piston you will see air bubbles coming true clear tubes that you have attached earlier to pipe ports and into filler neck. After Master is bled install it into the car. secure with two holding nuts and connect brake lines, tight brake line nuts so they do not leak when brake pedal is depressed. Star vehicle and feel brake pedal. If brake pedal is firm and do not travel more than two inches after application move slightly back and forth and try brakes. If brakes are OK you do not need further bleeding. if pedal is soft and travel down to floor you need to bleed brake system.
Use DOT -4 brake fluid.