How do you find a Fnet vs time graph from either a position vs time graph, Velocity vs time, or Acceleration vs time. I know how to find Velocity vs time to position and vice versa. since the slope of the position graph tells you the velocity. I can find a acceleration from Velocity. Since slope of velocity gives you acceleration. But how do you do this find a Fnet vs. time graph from Velocity vs Time. What would the varaible even be on the y axis.

Assuming that the acceleration you have in your Acceleration vs Time graph is the net acceleration, just multiply the acceleration by the mass of whatever it is you are studying to get a Net Force vs Time graph. F=ma ;).