Access the Swagger directly from the Clearing sUI by clicking on the rocket icon on the top bar
A new tab opens and you are now in the Swagger UI were you can try all API calls available from the Clearing UI
Authorization
First click on the Authorize button at the top of the table, then click the Authorize button on the popup box (as shown below)
Further documentation can be found in the Nord Pool Developers Portal: https://developers.nordpoolgroup.com/reference/cass-introduction