My bad! So, in Foundry when you go to "Install System" under game systems, this is the manifest URL you want to enter;
https://github.com/colearkenach/thefade-foundry/releases/download/v13/system.json
Yeah no problem, I'm actually submitting it to Foundry's system list;
https://foundryvtt.com/packages/thefade
It's going to be a few probably for them to approve it.
You shouldn't need to download it or unzip it, just putting the manifest URL in there and hitting "install" should be all you need to do! If it gives you trouble though, let me know.