Hi Gabriel,
Thank you for your query.
We found you have registered your Developer key with us and that's the only thing you need to start using our API.
For example: https://content.guardianapis.com/search?api-key=<your api key>
Kindly refer to api documentation for more information: https://open-platform.theguardian.com/documentation/
Please feel free to reach out to our team for any further information or query you may have.
Thank you!
Open Platform Team,
The Guardian.