Navigate to Google Cloud Platform and log in with a user with Admin permissions.

Create a new project:

Create a Service Account in your project via Menu > 'IAM & Admin' > 'Service Accounts':

Enter a name and continue.

Select role 'Owner' or 'Viewer':

Click done.

Save your Service Account email adress, you'll need it later.

Create a privateKey for your Service Account: Click on your Service Account name > KEYS > Add Key > Create a new key:

Keep Key Type = JSON. When you click on 'Create', a file will be downloaded with your privateKey.

The privateKey needs to be base64 encoded:

You can do this by going to base64encode.org. Paste your privateKey and click on encode.

Save your encoded privateKey somewhere safe, you'll need it later.

Using the email adress of your Service Account and the base64 encoded Private key, you can now create a new Source in dScribe.