Force all devices through VPN (without individual apps/software)

I have been able to download openvpn software on desktops and phones, and all successfully run through the ac88u as a server. What I cannot figure out is how to run the router so that all devices can connect to it as clients of the openvpn. So for example, items such as smart tv's and fire tv which cannot have openvpn software downloaded, will be able to connect through vpn.

I wanted to try and do this myself rather than paying for a VPN provider. Also have not found if Merlin or some...

Force all devices through VPN (without individual apps/software)