Hey kevin123. I'll do what I can.
I couldn't find any tutorials either.
Mark the wall exactly where you want the mounting screw to go. (we will assume it is not directly over a stud and that you are in between 2 studs.)
You are going to cut a hole. It will need to be about 5 to 6 inches high so you have room to handle it piece of wood and screw it into place. So your top cut will be about 3 inches above our mark, and your bottom cut will be about 3 inches below.
Start with the top cut (or bottom, doesn't matter). Start in the same center line as your mark. With a drywall knife, cut to the right.... keep going until you hit a stud. Then cut about a half inch further so that your piece of drywall will overlap the studs a little. This will help you a lot when you put the drywall back in place.
*Don't ram your saw all the way in. Just use the tip, no more than an inch deep in case there are any wires in there. (Insert penis jokes here) You do not want to cut or nick a live electrical wire.
Then go back to the starting point and continue along the same cut to the left until you hit a stud on the left side. Once again... cut a half inch past that first edge of the stud so your drywall piece will over lap the stud face a little on each side.
Do the same for the bottom line.
Then make your vertical drywall cuts to complete your rectangle and pop your piece of drywall out. Your rectangle should be somewhere around 16" x 6" depending on how far apart your studs are in the wall.
Measure your height for your screw again and mark it on each stud... you want to make sure the piece you a adding will be where you want it.
Measure the space between the two studs and cut a piece of 2x4 to fit. Before you put it in place, drill a 45 degree pilot hole in each end of the 2x4 on the side that will face out. (You can use the wide face of the 2x4 so you will have more surface area to screw into. You may want 2 pilot holes on each end if you do this.) Use a 2" or 2.5" screw to screw it into the studs. You can start the screws in the pilot holes so you don't have to fiddle with them while you are trying to hold the wood in place. (Don't drop it into the wall
Hold it in place, try and keep it flush, (it's okay if the piece is a little recessed, but its a pain the ass if it is a little proud) then screw in the one side.Counter sink the screw so that it doesn't stick out. Then do the other side also making sure it is flush.
Make sense? If not, fire me another question.
Steve