Follow instructions as per the post for installing the
Companion Mod
How to "install" the mod:
On PC: Extract the content of the attached zip file into the folder where you installed your Holiday Island main game.
(not into the folder named "game" , but into the folder where you have the game).
On a Mac: Navigate further down in the folder where you installed your Holiday Island game, until you see a folder named game.
Extract the content into this folder (not into the folder named "game", but into the folder where you have the game).
It will make a folder for images when you extract it.
That should solve your problem.