With your Internal connection, connect to your server-manager interface. Then select the
Security Remote access option. Near the top you will find a
Remote Management option where you can supply the IP address or range of IP address you will allow to connect to the Server-manager interface from the outside world. BE VERY CAREFUL, may cause significant problems if someone can hack your password.
Then to connect you need to specify
https://Your Domain/server-manager, supply your admin account and password and your in.
HTH,
Darin MacLachlan