License administrators have the ability to add, edit and deactivate colleagues in your organization as well as control the End Users assigned to a license. When you assign an End User to a supported license, that person will be able to access all relevant resources available from Zemax, and is authorized to run the licensed software. See the colleague and end user permissions article.
License and colleague administration is handled within your Zemax Profile page and you can also see what licenses you are administrator of. Note that the administrator of one license at your organization can manage other licenses as well, so the administrator of any license can "backup" other license admins if they are unavailable. See How do I add an End User to a license
License administrators are also who are sent license updates when the support or subscription is renewed or a licensed product is upgraded. It's therefore important to keep the administrator information up to date to ensure a license keeps working and eligible to run the latest software. If you need to change who the license administrator is, see this article.