Download the .mod file and patch it via this online tool (patch it on a vanilla us PM64 rom): https://hack64.net/tools/patcher.php
The more detailed instructions are on the itch page for the mod itself
thanks for the help cant wait to play :) one other question though can you keep the partner for the rest of the game as in like the game still functions beyond the extra boss fight and everything?
No I'm sorry, you're stuck in that one single boss room and you can't leave it.
