To add charms to equipment that has a charm quality, you need to invest in the Enchant Weapon skill.

Enchanting weapons/armour/items

There are also a couple quest related equipment upgrades.

The dragon breastplate can be upgraded by the dwarven smith...
once you have the dragonheart gem.

Silver Armour and Treasure Maps

Gathering the Holy Items and the Sacrifice

Last edited by Raze; 29/03/13 11:38 PM. Reason: update links