How do I make a free body diagram ?

To create a free body diagram, first you need to identify a body you are intrested in. Do you have it ? Great! Now lets draw this body isolated. I mean you don't want to include any object in its surroding into the diagram, only the object you are intrested in. If you've got that, you can then draw all the external forces acting on these body. Do not include any internal force. Now your free body diagram is ready.