Yeah, just mix the water to a volume that makes good sense for injection using a slin needle. Cant remember how much i used, its been so many years. 1cc is probably good. once its dissolved, figure your dose. For example, if the vial has 10 IUs in it, inject 1cc into it slowly and then swirl it around to mix. Let it dissolve completely. Try not to squirt the water right into the solid puck shaped solid in there(the GH), supposedly it can damage it. If youre taking 5 IU/day, then you would inject 1/2 cc into yourself and save the other 1/2 for the following day. keep it refrigerated, along with the undissolved vials too.
IM injection is a good way to go, or sub Q is fine. I dont think there really is much difference between the two. I know if you do sub Q though, you might get little bumps in your skin.