how to configure STC router, port forwarding

hi guys, i want connect home pc to head office through vpn tunnel, we r using DSL STC router, Model: Afaq Shamel 007.
I have configured RRAS VPN on window 2008 R2.it is working properly, i can connect LAN users but not internet users.
in router there is no option of port forwarding, but in NAT there are Port mapping and port triggering options available.
any support, suggestion will be highly appropriated.

thanks in advance.