So am I correct in assuming the pocket is already attached to your topcoat? If so, that really limits you on attaching the monogram. If you do not remove the pocket, you can use a fusible webbing and iron the monogram on the pocket and you can handsew a blanketstitch around the edge. If you were to take off the pocket and the fabric that the monogram is on is big enough, you can wrap the unfinished edge of the fabric around the pocket and then restitch the pocket back on. Or just remove the pocket and make your own pocket with the monogram fabric, using the current pocket as your pattern. Or if it’s not big enough, use the fusible webbing and do a machine satin stitch around the edges of fabric and then resew your pocket back on.