Port forwarding
As you may have seen in the server.conf, the OpenVPN server is listening on the port 1194
To access it from another location, you need to enable IP forwarding in your Internet router configuration
That’s to say, redirect <your_public_ip>:1194 to <your_raspberry_ip>:1194
I can’t help you more about this, it all depends on your router software
You’ll often find a NAT configuration page in the advanced options
Ask your Internet provider support if you don’t know how to do this