To create a line graph on a graphing calculator, the user must first ensure they are on the graph screen, then select the line tool from the menu and click enter. They can then place their pointer where they want the line to start, click enter to set the start point, move the pointer to draw the line, and click enter again to finish and lock in the line. Making sure to click enter after positioning the line is important as the line tool does not function like a pen.