There is a lot of variations to stay on top. It really depends on the person and what they are comfortable with. I will tell you a simple to stay on top. The rest really depend on you and your opponent what to achieve.
Step 1 - You are in his closed guard and your on top. You would sit on your foot with your elbows near his thigh and your hand near his upper abdomen. Your hand would create sort of a diamond shape.
Step 2 - Have your head up but not looking up in the sky. Face your opponent and relax. From here, the chess game begins.
