Could someone explain what that "power" stuff is for? Like how to get it, where to see how much you have and so on?
You gain power from leveling, opening up your inventory or crafting menu will display it on the left.
Power is basically like level requirements for items. It also gives you an idea of how good the item is. An unmodified, white-named item is going to be approximately equivalent in goodness as any other unmodified, white-named item of the same power. Items with different colored names/stars are better. You can adapt these items to your power level and they will be better than white-named items. You want to try and get all of your equipment to have a colored name/stars.