YOU NEED ADMIN SYSTEM FROM Rayman1103!!!
Link: http://www.gamemaps.com/details/9406
Install it here: C:\Program Files (x86)\Steam\steamapps\common\Left 4 Dead 2\left4dead2\addons

• 1) Start game with: -console (me i use: -dev -console)
  
• 2) Wait addon finish install
  
• 3) In the console:
  A:(copy)Bind "i" "show_menu Menu"(paste) and Submit
  B:(copy)Sv_cheats 1(paste) and Submit
  
• 4) Exit Game
  
• 5) Download SourceMod (GOOGLE IT)
  
• 6) Download Metamod (GOOGLE IT)
  
• 7) Download:
  https://mega.nz/#!k9VBmBRB!N2fAd8TcCQrDA3AdwARmSsI0rrtcRf7re9t70xpB0xU
  
• 8) Copy sourcemod + metamod + metamod.vdf into:
  C:\Program Files (x86)\Steam\steamapps\common\Left 4 Dead 2\left4dead2\addons
  
• 9) Start game with: -insecure (me i use: -dev -insecure)
  
• 10) Make OK, when a message appear, it's for said you cannot use Vac (official) Server
  
• 11) Play campagne or Surviaval or what u want; But select Local Server.
  
• 12) When you are in game use I (keyboard) and the menu appear.
  ENJOY!!!

I hope this help you, don't forget any numbers (1) 2) 3) ....)
And don't jump a line.

If you want play again on an official server:
C:\Program Files (x86)\Steam\steamapps\common\Left 4 Dead 2\left4dead2\addons

Select metamod (folder), Sourcemod (folder) and metamod.vdf (file) and cut them in an other folder for keep next or delete them.

If you need help for metamod or sorcemod, i can make you a link with them.