I have one of those - they call port forwarding something weird like "Virtual Server" or something. It's under the NAT section under Advanced.
The device can be configured as a virtual server so that remote users accessing Web or FTP services via the public IP address can be automatically redirected to local servers in the LAN network. Depending on the requested service (TCP/UDP port number), the device redirects the external service request to the appropriate server within the LAN network.
Virtual Server
Check this box to enable the virtual server function.
Rule Name
Enter a rule name or select an application name from the drop-down list on the right, then click the << button. If you select a predefined application name, the Public Port, Private Port, and Protocol Type are automatically configured.
DSL Interface
Select a DSL interface from the drop-down list.
Public Port
Enter the public port. This is the port seen from the WAN side.
Private Port
Enter the private port. This is the port being used by applications within your local network.
Protocol Type
Select the protocol from the drop-down list.
IP Address
Enter the local network IP address of the system hosting the server.
Time Schedule
Select a schedule when to use the virtual server or click the New Time Schedule button to create a new schedule.