Matillion ETL can integrate with other platform-specific services in your account, provided you have authorised it to do so. This is not compulsory, although some parts of the product (such as S3 and Cloud Storage) may not fully function without appropriate credentials.
Credentials can be added via Project → Manage Credentials and contains tabs for AWS and GCP, allowing users to input credentials for either platform. This will require users to access their platform's console and grant appropriate permissions for various services detailed in the links below.
For details on setting up AWS credentials in Matillion ETL, see here.
For details on setting up GCP credentials in Matillion ETL, see here.