How do you equip like 2 chest plates, or for a mage, 2 robes, for when I inspect someone, I see like 2 chesplates, or 2 leg plates, how do you do that? thanks
When you ding level 20 you'll have a new panel appear on your inventory window, the tab is titled "appearance". You can put armor here and it will override the visual for your gear. Nothing in the appearance slots affects your stats.
Only one of them is really being worn, meaning you (they) are only getting stats from one. The other is in the appearance tab and is just for show. As to how you do it... you just do it! The two positions should be side by side in the inventory window of your UI. (Unless your UI actually has an appearance tab in which case you'll have to select that tab to load armor into it)
In any case, the bottom line is that the appearance slots will let you appear to be dressed in clothes that have less than the best stats for your character. But it's all just for show.