If the wing is already covered, you'll have to at least cut away a good part of the bottom covering for this, but here's how I would do it.

First, cut the TE to form an aileron, leaving 1/8" of the balsa on the back of the wing. Then you will need to strengthen the remaining TE with 3/8" balsa blocks (These will also be needed to give the hinges something to grab on to). If the blocks stick out over the ribs, just sand them to shape once they are in place.

Now, you can either run torque rods to the center of the wing, or run nyrod out to the ailerons from the servo in the center (One servo per aileron would be overkill on such a small plane, but if you want to do that, go 4 it.)