Arthur Wright answered
Okay here goes. Using 12/2 w/ground romex wire. For another plug you will need 1 romes wire whether it comes from the existing plug or light switch is up to you as Ill tell you how to wire both ways. At the switch box you will need 2 romex wires, with 1 from the existing plug and the other from your light box. On the plugs, the black is your hot and attaches to the brass screw side and the whites are your neutrals and attach to the silver screw side and the bare copper wires go to the ground green screw. At the switch box; the whites go together and cap off as well as the copper wires too and push back into the back of the box. The remaining blacks whether two or three are as follows the light black is your switch leg and goes to the top of the switch and the other one or two is your power to switch and possibly other plug and both or one goes to the bottom screw and then just color code your lights wires to the light box wires and install all
