Every charged object emits an electric field that extends outward into the space that surrounds it. We call this charged object the source charge. To explore the source charge's electric force, we can bring a smaller test charge close to it and see how the test charge is effected. 

The Electrostatics Model that you've used doesn't model or show you the electric force field, but instead shows how two charges are effected by each other's electric force fields. For example, in the electrostatics model if you move a positive source charge closer to a positive test-charge, the test-charge will be repelled and move away from the source charge. You can think of the positive source charge as having a force field around it that determines how other charged particles that come close to it will behave. 

Make some guesses now: How can you visually represent the force field around the source charge in the Electrostatics Model? Run the model again and observe how the particles move in order to come up with one or more possible ways to visually represent the force field.