Creating a teleporter is SUPER easy. First, make a AAATRIGGER brush where ever you want you to teleport from. Right click on it, and click tie to entity. Make it a "trigger_teleport". Now, make a info_teleport_destination point entity where you want the destination to be. Name it something. Now, go back to the trigger_teleport brush properties and set the target to what you named your info_teleport_destination.