Extract the map to:

Steam\steamapps\common\portal 2\portal2\maps\

----------------------------------------

How to start the map in multiplayer:

Go to 
Steam\steamapps\common\portal 2\portal2\cfg\

start "config.cfg"

copy and paste this command in on the last line:

bind "KP_MINUS" "toggleconsole"

In your coop-game press keypad minus.
Now the console will open.
Enter this in your console:

changelevel mp_coop_fast_bridge_skotty

and have fun!



Map made by Skotty