Procedure for subscription and question about multple admis

Dear sir , i´d like to confirm that Premium version suports MFA, using for instance Google Authenticator.
If so, after making the payment, how do i change my free runnig version to Premium version ? Will I have to reinstall it?
One more question, can i have multple admins in this version?

Google Authenticator is available without a subscription for VPN users. An enterprise subscription is required to enabled it for administrators and to have multiple administrators. The license can be added and removed without effecting the running server.