When first using the Matomo Connector, Looker Studio will prompt you for credentials, specifically a Username and Token.
For the Username, please specify the URL to your Matomo. If your Matomo is located at
https://matomo.mysite.com, for example, you would enter
https://matomo.mysite.com within the Username field.
For the Token, please use a Matomo Auth Token, also known as a
token_auth, which are generated from within your Matomo. You can learn how to generate Matomo Auth Tokens in this FAQ.
For more information on connecting Matomo to Looker Studio you can follow the full connection guide here.