SHOULD come with an instruction sheet showing how to bench bleed. In addition, it should come with these little hoses/connectors. You install the reservoir onto the new mc and then hook the hoses/connectors up to the discharge ports of the mc and route the hoses to dump back into the reservoir. Put brake fluid in the reservoir and pump the rod on the mc until you do not get anymore air bubbles coming back through the tubes then install the mc on the booster. Keep level in the reservoir while you pumping.
This is the way I do it. Some techs may have a better way.
Jim