To create the angle bisector of ∠CAB, after placing the pointed end of the compass on point B and drawing an arc that intersects both lines AC and AB, the next step is:
Aubrianna must place the pointed end of the compass on point C and draw an arc between the angle above points C and B.
This step is necessary in order to find the points where the arcs from points B and C intersect, which will then help in constructing the angle bisector.