Setting up in Radiant
Download the prefabs and scripts then extract to root/map_source (PREFABS / SCRIPTS).
Place at least one of all included prefabs that should now be in root/map_source/_prefabs/zm/harrybo21_prefabs/.
Extract the scripts into root/usermaps/YOUR MAP NAME/scripts/zm/
There are 6 prefabs: the three teleporters, the mainframe, a 'black box room' that the players are moved to for a short time while teleporting (this MUST be covered by a zone - but out of sight - you can have another copy of your starting zone covering this) and a Pack-a-Punch cage prefab, which is optional and is what blocks your access to the Pack-a-Punch until the teleporters are activated on The Giant.
Setting up in script
Open your mapname.gsc and find this:
Underneath it put this:
Do the same in your mapname.csc.
Open your maps .zone (right click your map in launcher and click Open Zone File).
Add this to the bottom:
Recompile and test your map.