Downloading custom worlds

Hi everyone,

I was trying to download some custom world from the sims depot website which says to just download the link and open it, but after it’s downloaded my Mac says there’s no app to open the download and it won’t let me assign the sims 3 app to download it. Does anyone know how to download these?

Also, if you have any world recs (free of cc preferably so my computer doesn’t die lol) that are easy to download let me know!