Set it up
Visit script.google.com to open the script editor. (You'll need to be signed in to your Google account.) If this is the first time you've been to script.google.com, you'll be redirected to a page that introduces Apps Script. Click Start Scripting to proceed to the script editor.
A welcome screen will ask what kind of script you want to create. Click Blank Project or Close.
Delete any code in the script editor and paste in the code below.