Unwind and straighten the wire hanger as much as possible. All the curvature will not straighten out; straighten it enough to work with it.
Bend the wire hanger around the back of the performer's head, from above one ear to above the other ear, with equal lengths of wire extending beyond the ears on either side.
Bend the wire hanger down around the left ear and mark it at about the middle of the ear.
Bend the wire hanger down around the right ear. At about the middle of the ear make another bend, this one towards the performer's mouth. Mark the wire hanger at about 1/2-inch in from the corner of the mouth. This length of the wire, from ear to mouth, is the "boom."
Remove the wire from the performer's head, and cut the wire at the places you marked using wire cutters. Fully cover the cut ends of the wire with electrical tape, ensuring no sharp edges are exposed. This is the "headset."
Tape the lavalier microphone to the "headset" with electrical tape. Start with the element end of the lavalier, ensuring that the element itself overhangs the end of the "boom" by about half an inch. Continue taping the lavalier to the headset at 2-inch intervals, stopping midway between the ear curves.