Route some applications traffic to openvpn

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi all
I want to route some applications traffic to openvpn, such as instagram youtube and google play.
I setup openvpn client and declare one interface (tun0). all traffic routed to openvpn and i don't know how to route specified ip and subnets to vpn.

thanks very much

2

I think you underestimate the efforts required, but your keyword is policy based routing.