OpenVPN Site to Site

I am trying to set up a site-to-site configuration with OpenWRT and IPFire.
I have successfully set up the IPFire as the server and all devices are able to connect it it as such, including OpenWRT as the client. Unfortunately, I don't know how to route traffic on the OpenWRT router. If I try to ping the OpenWRT router from the IPFire server (OpenVPN address) it works fine, but I can't reach the local OpenWRT network even if I explicitly tell IPFire to ping through the OpenVPN address.

Any help is appreciated.