Somewhat story-related. You will unlock the Enchanter's Altar after you complete the main story campaign you'll get a super, super short quest to talk to an NPC to unlock the Alter so that you can build one at your Fort. Once this is done, gear will begin dropping that have a chance to contain an unfilled enchanting slot.
Before you can actually slot in an enchantment, you'll need a few things. The first are resources, which you can gain by breaking down weapons and gear at the Enchanting Altar. The second thing you'll need are actual enchanting recipes. These drop pretty frequently once you unlock the Alter.
With those two things, just add some enchantments to 25 different items with a free enchantment slot.