The forefinger is on top/side of the head, with middle finger pretty much underneath for support.
Thumb and ring finger are down the shaft a little ways....thumb on top....gentle pressure from below and above to cause slight tension.....make sure to avoid urethra, then push it in at a 90 degree angle.
He suggested doing it slightly below the circumcision line...or if uncircumcised, slightly below where the foreskin begins.
Hope this helps....my earlier description was off a bit....lol.
DanMan