The model below shows one possible representation of electric lines of force. Electric fields are typically represented as lines that point in the direction that a positive test charge would accelerate if placed upon the line. 

So, if you use test-protons (that have a positive charge) the lines are directed away from positively charged source charges and toward negatively charged source charges, and if you use test-electrons (that have a negative charge) the lines are directed toward positively charged source charges and away from negatively charged source charges. 

To create electric field lines and use the model:

1) Click SETUP then GO

2) Click ADD POSITIVE + SOURCE CHARGE. Drag the positive source charge anywhere in the black box. 

3) In the CREATE drop-down menu choose test-protons.

4) Click anywhere in the black box to test protons in the space you've created. Make sure to test many protons. Observe how the test proton charges behave in the space and how the electric field lines are drawn. 

5) Repeat with different numbers and positions of positive and negative source charges. You can do this by hitting the ADD POSITIVE + SOURCE CHARGE button and the ADD NEGATIVE - SOURCE CHARGE multiple times. Also, be sure to also test your space with test electrons, by selecting test-electrons in the CREATE drop-down menu.