How to install user Applescripts for Safari and activate the Scripts menu item?
You haven't specified the version of macOS or Safari you're running, but usually you would do this:


In the Finder, go to the top level of your Mac's hard drive (or SSD)
Navigate to /System/Library/CoreServices/Menu Extras/
Double-click on the Script Menu.menu file


This should add the Script Menu to a number of supported apps, etc.