Press the arrow. Nucleus Co-op will begin opening multiple instances of the game and automatically resizing them. In-Game Setup (Zombies) :
: Version 1.0 supports two-player Zombies mode offline.
The Steam version does not have a "Local Play" button on the main menu. You must load into the mode directly via the console.
Copy the fix files into the main directory where BlackOps.exe is located.
: If instances won't connect, you may need to temporarily disable your Windows Firewall or add an exception for Black Ops.