This Location has no building cost so you can build it for free, but it still requires you spend your turn taking the Build Location action. The Ruins card has no type (color), nor can it be razed.
When you activate its Action you immediately build a Faction Location. You still have to pay the building cost of the Location, except that you do not discard a Location from your Empire if it's required.
According to the rules when you activate an Action Location you place the Goods spent on the Location card, but covering the Location with another card would be very inconvenient, so we recommend to discard the card and take a Worker from the general supply to indicate that the Action was executed.
If you're playing the Japanese and you have Deals with enemy Locations (due to the Trade Route card), you can also choose such a Deal when you activate this Location's Action.
If you're playing the Japanese and you have Deals with any enemy Locations (due to the Trade Route card), you can cancel such a Deal instead of discarding a Deal from under your Faction board when you activate this Location's Action.
You can choose either a Common or a Faction Location when you use this Location's Action.