You don't need a workshop to charm an item, just to enchant / un-enchant.
With the Xbox version, just select a piece of equipment with one or more empty charm slots in the inventory and hit A; a menu will come up allowing you to permanently charm the item with any of the charms you have collected. In the equipment menu you can hit Y to add charms to equipped items.
On the PC, right click a piece of equipment with an empty charm slot.
