Open your Black Ops III game folder (see the default path above if you’re unsure).
Move t7x.exe into that folder next to BlackOps3.exe.
Run t7x.exe once. It will set up the client automatically; let it finish.
Launch the game through t7x.exe going forward (you can make a desktop shortcut).
Notes
The client checks Steam ownership and integrates with the official online services. Bypassing these checks isn’t supported and will prevent it from working.
Keep Steam running when you start the client.
Optional: Verify it worked
After launching via t7x.exe, you should see T7x-specific branding or version text.
You should be able to browse servers/playlists normally from within the game.
Troubleshooting
If the game starts as stock BO3, make sure you launched from t7x.exe inside the game directory (not from your Steam library shortcut).
If the launcher can’t find the game, confirm the folder path and that you moved t7x.exe into the same directory as the game’s executable.