1) Open router's administration interface in your web browser. Follow instructions on image below. Important is to choose PPTP as Wan Connection Type. VPN username, VPN password and Server address are shown above.
2) Click on Network Map and check if Internet status is Connected.
3) OPTIONAL: If you want to make any device inside your local network visible from the Internet, you need to set Port Forwarding. You need to know IP address of your device and port that service runs on. Enter this details in Local IP and Local port field. Enter desired port in Port range field that will be forwarded to Local port. (e.g. port forwarding set on image below forwards every request from the Interet to port 5400 to local device with IP 192.168.1.192 and port 5400)