Plan the placement of the bead molding on the wall panel, and use a measuring tape to decide how long your molding pieces should be. If you intend to make square shapes with the molding, remember that you'll have to miter the corners, so you'll need to measure to the long angle of the mitered edges.
Cut your bead molding pieces according to your measurements. Use a miter saw or a table saw to cut the pieces. Always wear protective eyewear and work gloves when using saws.
Sand the cut edges of the bead molding until they are smooth.
Stain or paint the bead molding. If you paint it, apply a coat of primer, and allow the primer to dry for at least 2 hours before applying the top coat of paint. If you stain it to match the existing panel, test the stain on a scrap piece of wood before committing to staining all of the bead molding. Allow stained wood to dry overnight before proceeding to the next step.
Use finishing nails and a small hammer to attach the bead molding to the wall. Sink the nails below the surface of the molding to hide them.
Fill the nail holes in with wood filler, and wipe away any excess. Allow the wood filler to dry overnight and then sand any rough spots over the filled holes.
Touch up the paint or stain over the filled-in nail holes on the bead molding.