Log in to your control panel and select appropriate subscription.
Then go to "Cloud" and click on the name of the server you want to configurate.
Go to "Firewall" tab and click "Add" to add a new rule.
Fill out new custom firewall rule form and click "Add".
Remote IP: client's IP
Any: Allow access from all IP addresses.
Address: Specified the allowed IP address of the client.
Netmask: Limit to specified range of the network.
Protocol: Select protocol to which the rule applies (TCP / UDP).
Remote port: Allow connection originating from the given port.
Local port: Allow connection to given port.
Be careful when creating new firewall rules, as any connection that does not strictly comply with any of the firewall rules will be blocked .
Example : Allowing only remote desktop access from one specified address.