To manage the Trusted Certificates in the IoT Server, navigate to the left bar menu in the IoT Server Configuration and select the entry labeled Certificate management. This section provides the functionality to edit and adjust the list of trusted certificates.
To Create your first trusted certificate
In the certificate management page, copy and paste your private key text encoded, if you multiple certificates, just append them one after the other.

To manage the trusted certificates after registering the first one, click on Edit (1) button:
This displays the certificates in text area you can edit.
To remove a certificate, locate and delete its text from the text area. Once you've made your updates, be sure to click the Save button. A green notification will appear to confirm your changes.
Rq: When you have a single certificate in the library, to delete it, you can also use the Delete button (2) in the main page. Confirm choice in the confirmation popup.