Installing the sp_simulacra.
1) When you open the archive, there are two folders. One of them is "maps" and another one is "materials".
2)First copy content of the "maps" folder (there is only one file there - sp_simulacra.bsp) and paste it here: C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps
3)Copy all texture files from "materials" folder and paste it here:
C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\materials
4) Run Portal 2, on console type this without quotes "map sp_simulacra" and press enter.
About Simulacra:
Gametype:Singleplayer.
Genre/Theme: Abstract.
Gameplay: Trial and death.
File Name: wsp_simulacra.RAR
File Size: 3.27 MiB
Click here to download sp_simulacra

I actually got more put off by reading the comment about not knowing where to place a portal because I agreed at first when I couldnt work it out then I cleared my head and thought out of my box.