Answer
See the picture below:
Work Step by Step
With your compass mark an arc to intersect both sides of $\angle MRP$.
With the same radius, mark another arc with the center of point $O$ to intersect $\overline{OA}$ (at point $E$) and the future $\overline{OB}$ side.
Mark an arc to measure the distance from C to D.
With the same radius mark an arc from point $E$, and intersect the other arc. The point of intersection will be point $B$
Connect $B$ and $O$ to get the other side of the angle.
