To connect Agility with Google Analytics, you must have a private key file (JSON) associated with a service account that is authorized to access your Google Analytics account.
To generate this key, you need to create or use an existing project in the Google Developers Console. Go to https://console.developers.google.com to create or select a project. Ensure that the the Google Analytics and Analytics Reporting APIs are enabled for the project.
More information: Enable and disable APIs - API Console Help (google.com).
Then, create a service account and generate a JSON key.
More information: Creating and managing service account keys | Cloud IAM Documentation (google.com).
Before uploading the JSON key to Agility, log into your Google Analytics account and add the service account email as a user with read/analyze permissions.
More information: Google Analytics user permissions - Analytics Help
Once complete, you can upload the service key to your Agility account on the Data Connector Page.