To be able to use Google's Oauth2 authentication and use altruist's actions like youtube or googledrive, you will need to create a Google API Console project.
Go to Google API Console and create a new project.
When your project is created, click on Credentials and select OAuth consent screen. You'll have to provide an email adress and a product name.
After that, create new credentials for this project and select OAuth client ID and Web application.
In Authorized redirect URI, you have to a URI that matches the altruist action's callbackURL, then create the credentials.
You will be prompted your client ID and client secret. Put them in settings.json.
The redirect URI might take a few minutes before you can use it.
Depending on what google API is used in the altruist action, you will have to activate them in Google API console. Click on library, select the API you want to use, activate it, and it's done !