How does cross sectional area of the resistor affect the value of resistance?
Since you cannot measure resistance directly, you will need to measure current (using your multimeter) and then calculate resistance using V=IR. Remember, your goal in this lab is to measure the relationship between cross sectional area and resistance. These are the two variables that should be in your graph and data table. What you will be actually measuring in the lab is cross sectional area and current. Once you write down the value of current in each measurement, a group member should immediately calculate resistance, since that's what you actually want.
Change the cross sectional area of the resistor (pencil lead) by grabbing a new piece of thicker or thinner lead each time. You may not get enough data points to be confident about your trend, but you may be able to see a trend if you do your lab to the best of your ability.