1. Hang archway strips
Cut two strips of matching paper, equal to the height of the archway and as wide as the jamb's depth, and hang them. Just below the curve, make a horizontal cut in each side strip from the inner edge to within 1 inch of the wall. Wrap the lower portions of each side strip around the arch’s edge, and smooth.

2. Trim & match
Using utility shears or scissors, trim the unsmoothed paper on the archway to within 1 inch of the edge and then make small, wedge- shaped cuts in it to within 1/4 inch of the edge. Measure the length of the arch and then divide that length in two. Cut two matched strips for the arch 1/4 inch narrower than the arch depth (to prevent fraying) and 1/4 inch longer than each divided length. Apply the strips from side to top and then double-cut the seam.