If you don't see the license management page or the field to enter an entitlement key is grayed out, this means you don't have the proper permissions to add an entitlement key. You would need to log in as a super admin to add entitlement keys. If you can send me your VHM ID I can let you know who your current super admins are and how to make new ones. My directly email is communityhelp@aerohive.com.
If you are using HiveManager Classic (myhive.aerohive.com), you can find your VHM ID in Help> About HiveManager.
If you are using HiveManager (formerly NG, cloud.aerohive.com) you can find your VHM ID by clicking on the silhouette icon> Global Settings> VHM Management.
