Are you on Mac? You need to make the name of the app "CrabGame", copy it, then go to the Steam library folder (Finder toolbar > Go > Go to Folder > "~/Library/Application Support/Steam/steamapps/common/Crab Game" ), and paste it (replace old one). Then you need to run "Play" from Steam.
This is Steps 9-11 in this install guide: https://itch.io/post/4880634
Also make sure it's 64Bit version. Some people having issues with Silicon even after installing.