To access data from a Google Sheet with your app, you will need to create a service account and download a credentials file from the Google API Console.
- Create a Google spreadsheet.
- Go to the Google APIs Console.
- Create a new project and navigate to it.
- Click Enable APIs and Services. Enable the Google Drive API.
- In the Create credentials options, select Help me choose. You are using "Google Drive API" from a "Web server" to access "Application data".
- Add credentials to your project. Name the service account and grant it a Role of "Project" > "Editor".