i have RV042 VPN router i want to know how to configure in vpn i try to configure but not working. pptp is working but only inside the network using other network not working

i have problem with my cisco RV042 PPTP VPN connection.. the vpn is working inside the network but if i use another network and trying to connect with my pptp vpn connection is not working at all i don't know what is my missing configuration.note:ins...