Firstly, you have to destroy the item with the enchant you want in order to learn it. Thankfully, the enchant will be forever available to put on your gear from now on. Unfortunately, the amount of bonus you get from it is entirely dependent on the tier/level of soul gem you use. So early on, I'd recommend using the enchanted stuff you find until you get a replacement BEFORE sharding it, as you'll get more use out of it then, since you don't have access to higher level soul gems and souls.
"When the sword becomes a burden, let the warrior lay it aside so that another with a truer heart my take it up." -Radiant, Archangel