Welcome to the forums. Honda GN4, 10W-40 is the recommended oil, but you can use other brands of oil, as long as it is safe for wet clutches. Avoid using automotive oils that are energy conserving or that contain friction modifiers as this will cause the clutch to start slipping.
The clutch free play adjustment is on the right side of the engine, under where the oil filter goes. It should have a black plastic cap over the adjusting bolt, unless it's missing. To adjust, loosen the locknut. Slowly turn the adjusting screw counterclockwise until you feel resistance. Now, turn the adjusting screw clockwise 1/4 turn. Hold the adjusting screw while tightening the locknut back down.