you have to make a teleport (the place you want to step on for the teleport, i believe its a func_teleport entity) then you also make a teleport destination where you want to be teleported (func_teleport_dest i think) then you set the entity properties of your teleporter to
"target" "<yourtarget>"
and the teleporter destination to
"targetname" "<yourtarget>"
you can use any combination of #'s letters and other things for <yourtarget>, just make sure
they are the same.
also, make sure you set "angle" on the teleport destination to the right angle so you will face the right way
and it is impossible to change the size of the teleporters, which really needs to be fixed
hint hint jitspoe

for now you just need to make a wall of teleporters and destinations if you want to have a larger teleport.