The raw edge of the fabric must be secured with a seam finish either before or after attaching trim to the edge of your table cloth.
If the trim you will be attaching is pre-finished on both edges it is possible to attach it over a finished edge. Hem, zigzag or serge the raw edge of the table cloth before attaching the trim.
If one edge of the trim is not finished place the right sides of the trim and fabric together to sew on the trim. Zigzag or serge the raw edges together. Press the seam allowance toward the body of the tablecloth and top stitch the hem to the body of the tablecloth.