GH is something that you want to stay on long term, while you cycle steroids on and off. Steroids will have a faster effect but gh will keep producing a good response long term. I would suggest using gh for no less than a few months, or up to a year or more at a time. I use it for about 11-12 months a year, then take 1 month off.
As for how to inject, you can do either Sub q or IM. I suggest IM. Blood levels will go higher with IM shots. I suggest using a 1/2 in insulin pin, and injecting in an area with little fat like the tricep or delt. At 4iu, if you train in the afternoon or evening, I would take 2iu in the morning. Then 2iu preworkout