Fix DNS leak (from VyprVPN's CLI)

I'm using VyprVPN's CLI, connected to a server overseas. But my DNS is leaking (I used this site to check).

I've found several answers for this question, but there were all for the manual configuration of OpenVPN—not using VyprVPN's CLI.

I've tried to figure it out but I'm not sure how the CLI works, or even where to find the configuration files for it. I've contacted customer support, too, but they wouldn't offer any help other than linking me to where I can download their .ovpn configuration files.

How can I configure my VPN / network connection to stop leaking my DNS?

Other details

OS: Ubuntu 17.04