Go to Advanced > NAT > Port Forwarding and click Add.
Enter the Service Name, the LAN IP of the destination device, External Port, Internal Port, and Protocol (TCP/UDP).
Check Enable and click Save & Apply.
Warning: For Port Forwarding to function, the Firewall level must be set to Low (default). Check Security > Firewall > Firewall Level. Also ensure the destination device has a fixed LAN IP — configure a Static DHCP entry in Network > LAN Configuration > IPv4 Configuration.
Tips: For applications that open ports automatically (games, VoIP, file sharing), enable UPnP in Advanced > UPnP.