First off, you’ll need an OpenVPN setup on your server to connect to.
Then you’ll need to install the OpenVPN Connect on the phone.
Use the typical config files that you would on an OpenVPN client. Just rename it to
client-name.ovpn where “client-name” is the name of your device.
Copy the files and the config to you sd card.
I had some trouble with the app not being able to import the files. I had to put the files in the same folder and then adjusted some of the config options as follows.
tls-auth ta.key 1