1. Buy the game from Steam. https://psteamproxy.yuanyoumao.com/app/12200/Bully_Scholarship_Edition/
2. Install the game.
3. Right click the game in your Steam library and go to properties. Select Browse Local Files.
4. Download Bully Multiplayer here http://www.bully-mp.com/
5. Unzip the folder and copy the files into the local folder for the Bully game.
6. Run BullyMP.exe.
7. Select the Bully.exe from your local folder for the Bully game.
8. You should now be running the Bully Multiplayer.

Hopefully the mod will become more popular and it will receive more updates.