ok Dumb Newbie Question on GH

[Gettingbiggg]

This is the first time I've been running it, I finished week 4. I have been doing sub. Ive been reading on the IM. Whats the difference and benefit?
Also again a newbie on this stuff. IM so I just take the insulin needle and stick what ever muscle I choose? and the needle being so short will be deep enough to hit the muscle.
I do already inject my tes in my biceps to alternate injection sites. quads, ass, biceps are my normal injection sites for my tes.

Sorry for the dumb question lol