1. Navigate to wherever you have Sifu installed and go to it's Paks folder
Example: D:\SIFU\Sifu\Content\Paks
2. If it doesn't exist, make a new folder called ~mods - Should look like this: D:\SIFU\Sifu\Content\Paks\~mods
3. Drop the mod's pak and sig files in there
4. Boot up the game and have fun!