If you still have the first teleporter stone, you can drop and use it to get to the second. Then stand near, click on it, drag into your inventory and release the mouse button. You can use the teleporter stone without dropping it to get back out (click on it in your inventory, or click on the active skill/special move icon on the menu bar - there are three options for using the teleporters on the right hand side).
If you don't have the first one, return to the fourth level of the catacombs. On the western side of the door is a lever to unlock it, for those who did not want to use the first teleporter stone and end up in an unknown location.