Once logged in, select 'Virtual Servers' on the lefthand menu under 'Appliances'
Click on the name of the server you wish to edit the firewall rules,
On the menu at the top of the screen showing 'Overview', 'Networking', etc. Select 'Networking' and then 'Firewall'.
This will then show the current firewall rules, as well as options to modify these.
To add a rule, enter the required settings under 'Add a Firewall Rule' and then click 'Add Rule'.
Under 'Firewall Rules', you can remove a firewall rule by ticking the rules and selecting 'Remove Selected'. You can also remove an individual rule by selecting the trashcan icon. To edit a rule select the pencil icon.
The 'Default Firewall Rules' allows you to control the default behaviour of the firewall. If changed, select 'Save Default Firewall Rules'.
To apply any changes make sure to select 'Apply Firewall Rules'.
You can verify the changes by trying to do anything that has just been blocked or allowed.