using line of best fit to find g lab

Procedure was to prop up a board at angle theta put a “smartcart” at the bottom (which measures everything for me) and press the button on the smartcart activating a plunger that propels the cart up the board. We were told that somewhere along the way of finding g we are required to vary something in our procedure to produce data and create a line of best fit. we decided to vary the force that the plunger pushes on the ground so that the distance to the peak would change. so now i’m at the point where i have all my data and i don’t know what the next step is (aka how to create some graph that i could make a line of best fit for and solve for g). any help would be great