Use the segment tool to draw segment AB (make it at least 3 inches long)
Use the point tool to mark point C near A (within half and inch or so)
Use the perpendicular line tool to construct a perpendicular line through C (first click on AB, then click on C)
Draw in four points (D, E, F, and G) between C and B.
Use the semi-circle tool to draw a semi circle from A to D, then D to A. Repeat for A to E, then E to A and so on, ending on A to B then B to A so you have drawn 5 circles.
Label the 10 intersection points of the circles to the perpendicular line using the intersection tool. Click on the circle and then the perpendicular line above the line from smallest circle to highest H, I , J, K ,L. Repeat below the line from smallest circle to largest, M, N, O, P, Q.
Use the parallel line tool to draw parallel lines to AB through the 10 points on the perpendicular line (click on AB then point H and repeat for each point)
Use the perpendicular line tool to draw perpendicular lines to AB through D, E, F, G, and B (click on AB then D and repeat for each point).
Use the intersection tool to label where the perpendicular line through point D intersects with the parallel line through H and M (click on the line through D and the line through H, then click on the line through D and the line through M). Then repeat this process for E through B moving up one point on the perpendicular line every time you move over one point on AB.
Use the Freehand Shape tool to connect the intersection points that you labeled in step 9 and include point C. You have constructed a parabola!