First you must step into the teleporter (the gold or blue areas inside them) to activate it, then it will pull up this map window with a list of where you can teleport to. You can close it if you step in by mistake by clicking the x (marked yellow). You chose the destination by either clicking the little blue dot on the map, or the name on the list to the left. Then you activate by clicking the teleport button (marked purple). You can zoom in or out of the map for a better view using the zoom buttons (marked red). If you are on one continent and wish to go to the other click the change button (marked black).