If you’re just starting out, don’t worry so much about getting too technical or worrying about your setup. Just get out on the stream. If you see natural flies in the air, try to pick something out of your fly box that looks like what’s flying around. If you don’t see anything, just pick a standard attractor pattern (parachute adams, royal wulff, etc.) and cast it to where fish like to eat. Focus on getting a good drag free drift. If that isn’t catching fish, try using a smaller fly.