Question VPN and Asus RT-AC68P

Trying to figure out how to install VPNPro into my Asus router.
It asks for Import .ovpn file ?
Where do I find this file?
A VPN has two sides. Client or server.
A VPN server on your Asus would provide secure remote access to your LAN.
A VPN client would allow your LAN devices to route traffic through a remote server.
Which end are you trying to configure?
 
I'm trying to add secure access to all devices that connected to router by wireless and cable
"Secure access to" means, to me remote access to your devices. Is that what you are trying to do?
If so, then you need to configure a VPN SERVER on your router.
A ".ovpn" file would be if you were trying to connect to a remote VPN server as a client. Do you have a subscription to a VPN service ?