After connecting to the GCP shell, I followed the procedure shown until typing gsutil ls.
Then I had the following error message: ServiceException: 401 Anonymous caller does not have storage.buckets.list access to the Google Cloud project.
After calling my bf Google, I found the following procedure:
1. Type "gcloud auth login" & "enter"
2. Click on the link provided and chose the account you used to login the GCP console.
3. Click on "Approve"
4. Copy the link provided on the web page and paste it on the shell.
5. Press "enter" and voilà.