Find your credentials on the dashboard

Credentials are accessible once you have filled in the sandbox account creation form.

You will then receive an e-mail inviting you to create a password. Once you've entered your password, you can access the test dashboard at the following address:

This takes you to your home page: 

To retrieve your credentials, simply go to the PARTNER tab and click on SECURITY :

You can find the documentation to support you throughout the integration process here