Gedman--
Gave myself my first one on Monday.
Instructions I have are to inject in the back half of the shaft (between your body and half-way toward the tip) between the 2-3 or 9-10 o'clock orientations, avoiding any visible veins.
As short as I feel right now, that didn't leave much of a target area for me.
Good luck with the first one on your own!
--Steve