To install a new electrical control panel, shut off the electrical service, mark all of the wires, disconnect and remove the breakers and the old panel, mount the new electrical control panel, and reconnect the wiring to install a new electrical control panel. Some of the procedures vary depending on the type of electrical panel being replaced and installed.
If the house is equipped with a main service disconnect bar located before the electrical panel to be replaced, throw it to disconnect the power coming to the panel. Call the utility company, and have them disconnect the power if there is no service disconnect switch.
Carefully label all of the wires coming into the box according to the area of the house and specific appliances serviced by each. If the old panel is clearly marked, you can copy the labeling; if it isn't, you must trace the wires to find out where each one leads. The house electrical system can't be installed with the proper size of breakers if you don't know the electrical requirements for the lines.
If the new electrical control panel is larger than the one being replaced, or if the old panel is an outdated fuse box, make a new mounting plate by cutting a piece of 3/4-inch plywood slightly larger than the new electrical panel. Firmly screw the new plywood to the home's studs, and mount the new panel squarely to the plywood. Transfer the wire label information to the grid inside the new panel's cover door.