The standard supplied plastic jigs are best suited to engraving the Ladies Charm. Centrally locate the charm into the V-grooves of the jig, then open a 16mm x 23mm oval/circle shape. Using the vice with whichever jig suits you best, is probably the best option for engraving the Gents Bracelet - Mount the engravable bracelet so you can engrave it Left-to-Right.
Care MUST be taken to secure and position the engravable bracelet whichever method is used.