Basically, a protractor is used to measure angles. You probably have a semi-circle shaped one. Looking at the bottom middle of the protractor should show you lines intersecting each other at a point. If you have an angle on a piece of paper, place that point on the ends of the line segments making up the angle. Then, check where each line of the angle crosses the numbers on the outer rim. That shows you the measure of the angle you are examining. It can be a bit tricky, but with practice you'll get it in no time!
