You can add a lien holder or loss payee during the quote process, when adding the vehicle information. Once you checked the box for to add comp and collision, a field at the bottom will appear to enter the lien holder's info.
Once the policy is active, you can the lien holder by selecting the "Manage Fleet" button on your INSHUR dashboard. For more info on managing your fleet, please review this article
You will need the following info:
Lien holder name
Address