Sorry if this is an obvious question, but I can't find anything online that answers it. You can equip several artifacts on your character sheet. They talk about doing damage to your enemies. How do you USE them, as in, assign them to a button in your HUD? What if you have more than one artifact? Do they each get a button?
Everything else, like in the Powers screen, clearly says, "Click here to equip to your HUD", but there is nothing about artifacts that I can find in the game.