There are many things that control teleporting. One of them is ELEMENTS.DATA. Inside elements.data I believe is where you would control which teleport points 'connect' to which points, and how much 'coin' it 'costs' to utilize the teleport... Then there is TASKS.DATA if you want the "geographic map" to properly add any additional points that you may create/add. Then there is WORLD_TARGETS.TXT on the client side and WORLD_TARGETS.SEV on the server side... Which lists all the teleport coordinates. Then of course a combination of ELEMENTS.DATA and NPCGEN.DATA to control the location for the teleporter NPC's to 'spawn'... That is all I remember / can think of off hand, there is no 'straight up' tutorial to my knowledge, but I'm sure if you look at every file I mentioned (and search the board, as some things related to this have already been answered) you'll be able to figure it out
Add: By no means did I say it would be "easy" either though. If you want to add even just ONE teleport 'point' you're going to have a shit-load of work on a crap-ton of files to do
