Setting the Flywheel timing on a Honda 150cc Lawnmower Engine?

I took an old Honda G150 apart and am now putting it back together and I'm not sure how to get the flywheel timed properly. Can anyone just give me a basic walk through on how to time the flywheel?

IT SHOULD ONLY GO BACK ON ONE WAY. A PIECE OF METAL LINES THE TWO PARTS UP RIGHT.