How do I manage multiple Security Center accounts in OnPrem?

From within your Organizer, you can add multiple Security Center accounts to get a better structure and overview of all your accounts/networks, you can add users to manage the different accounts in Organizer and assign users to certain Security Centers. Superusers in Organizer can setup usage limits and manage the amount of assets being used for each Security Center. 

You can read more about how to create an account here: How do I create a Security Center account in OnPrem