Youtube a few videos of it, typically there ar 15's but the process is the same. Once you see a few, and a couple of different methods they use, you'll see its not that complex a deal. I've seen a few with no torque wrench, and just lining up the gas tube holes once its fairly snug. Then there's the "do it three times" camp, where you tighten to spec, line the hole, then undo it all and repeat it two more times. So watch a few, pick one you think is good and use that. Im a fan of torquing to the lowest spec, then twisting to the next hole lines up, being sure not to exceed the max spec.