Download the Scratch app form official website
https://scratch.mit.edu/download
Detail
Install the Scratch app for Android (Android tablet user)
https://play.google.com/store/apps/details?id=org.scratch
Install the Scratch app for Windows (Windows PC)
https://www.microsoft.com/store/apps/9pfgj25jl6x3?cid=storebadge&ocid=badge
or
https://downloads.scratch.mit.edu/desktop/Scratch%20Setup.exe
Install the Scratch app for macOS (MacBook user)
https://apps.apple.com/us/app/scratch-desktop/id1446785996?mt=12
or