thats to get to the clutch bearing. He wants to see the timing mark on the flywheel. You dont unscrew that big green nut, you should have a plastic cover on that (either its missing or you have taken it off. On the flywheel you should have a v shape mark, thats your itming mark on the flywheel. You turn the engine over by hand to find it. Other way is to take out the 1st spark plug (left side) gently put a screw driver inside it and turn the engine by hand till the screw driver is at its highest point. Make sure ur timing belt is still on