Paul, the simple solution is, you must find another receptacle to tap
off of, don't use the wires going to the switch. Just find another
receptacle, fish the cable to that box, connect color to color on the
receptacle or the splices in the box that tap off to the receptacle.
the only way you could tap off a switch box is if there are 2 or more
white wires in that box spliced together that are not connected to the
switch. In that case, you tap off the black wire on the switch and the
white wires spliced together.
Incidentally, if you ever extend a circuit by tapping off an existing
circuit, don't use the little holes in the back of a receptacle for
extending to a new branch that will have several receptacles on it.
Those cheapey connections aren't worth a hoot for carrying current.
Splice the wires in the box with wire nuts along with a black and
white wire, short pigtails, that you will connect the receptacle back
Agree with you getting a book from Lowe's or somewhere on DIY