Convert OpenVPN config files to the ONC ChromeOS network config files.
Download the ovpn2onc.html file and open it in Chrome (or any other modern browser). Follow the instructions there.
You can also use the hosted copy at https://thomkeh.github.io/ovpn2onc/ovpn2onc.html but be aware that in this case your configuration (with keys) will be sent over the Internet and you have to trust the website.