On this surface mounted porch light, there is a green wire (ground) and a thin stranded wire. Do I attach both of these to the circuit ground #14 wire and then pigtail from there to the green ground screw in the metal box?? Or do I attach the green #14 to the incoming and outgoing ground #14, and just attach the thin stranded wire to the ground screw. I hope I am making some sense!

Just as long as all the bare and green wires are connected together, in any fashion or order, and connect to any metal box, or fixture bar, then you will be fine.