1. Navigate to Services | UPnP and NAT-PnP.
2. Check the Enable UPnP and NAT-PnP checkbox.
3. Check the Allow UPnP Port Mapping checkbox, or the Allow NAT-PnP Port Mapping checkbox, or both:

4. In the Interfaces list, select the interfaces to which UPnP/NAT-PnP will be applied.
5. When you are done making changes, click on the Save button.