Preparation - NoSubstitute/userDelegationWebApp GitHub Wiki

There are a few steps before you can use the library in your script.

If you copy my template script you can skip some steps, but read through them anyway just to verify that your script looks ok.

If you don't copy my template you will have to create a script with the many files and manually copy all the scripts content into the Apps Script editor before going on to step 1.

Copying the template is much less work. I promise.

1. Add library and Gmail service
2. Create project
3. Enable Gmail API
4. Create Oauth credentials
5. Assign project to your script
6. Get Service Account JSON keys