Hi, I decided to try out making a desktop pet and I imported the extension into my project, and I can't get it to run. I don't know if I'm just a dummy and I'm doing something seriously wrong or what

Custom window shapes for GameMaker games! · By
That usually means that GameMaker ate the file names in the extension. If you double-click window_shape in the resource tree, it should show them like this:

If there are empty spots instead, you can double-click on each file and assign the correct name in the “Name:” field. You can tell which one’s which based on function lists (pictured).