You can drop and use the first teleporter stone to teleport to the second, which you can then pick up after clearing out the skeletons (stand close, then drag and drop it into your inventory window or onto the menu interface along the bottom of the screen). Next you can use (without dropping) the second teleporter stone to get back to the first (click the 'use' skill icon, or click on it in your inventory). Finally, pick up the first teleporter stone, head to your current home base, drop one teleporter stone, and keep the other with you.
If you just use the first teleporter stone to get to the second, there is a teleporter pad in the room (in the hallway to the south west), which will bring you to the start of the catacombs.
When you are exploring and want to get back to base quickly (to sleep or drop off loot when encumbered), you can drop and use the teleporter with you, do whatever, use the teleporter at your base to get back, pick up that teleporter stone, and keep going.
