How do I transcribe an AppleScript?
You might be making this more complicated than it needs to be. If you want the code from the other site in an applescript, that page provides guidance. You don't need Automator to simply run that script.

Copy the script text onto the clipboard. Launch the Script Editor. It should open a new and empty document. Paste the copied script. The text should appear as whatever your default is for new (or uncompiled) text, e.g. probably in a purple monospaced font.

Confirm that everything is hunky dory by compiling the script: Type Command-K (or from the menus: Script > Compile). It should take on the same appearance as what you saw on the other site, e.g. some words coloured or bolded (emboldened?). Depending upon whatever, you may find that the quotation marks have been altered and you get an error. They need to be straight double quotation marks, e.g. "" and not “”.

Then try it out. If it works as desired, save it somewhere easy to access, e.g. the Safari scripts folder. Then, if you have the Script menu enabled (check the box in the Script Editor General preferences), you will be able to run the script from the script icon that shows up on the right end of the menu bar (near the clock) whenever Safari is the active app.

/Users/username/Library/Scripts/Applications/Safari


NB I'd suggest saving it as a script (as opposed to application) unless you have a specific need that requires that.