To permanently add a charm:
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 (currently that is the only way to charm a bow).
On the PC right click a piece of equipment with an empty charm slot.
About the other question you posted in the BD forum: training a skill increases the level cap for the skill, but does not increase your current level. You still need to put skill points into the spell/skill yourself.
In the top left of each forum index (such as the D2:ED Help/Tips/Tricks
forum), there is a 'New Topic' button (left of the page number listing, just below the main forum index in gold text) which you can use to start a new topic.
Searching probably would have given you an answer quicker in this case, as well, assuming you noticed the default search range was only a week, and increased that.
Welcome to the forum.