Just plug the HDMI into a 4k TV, that's it.
Not sure what the guy was talking about the video card converts it to 1080p, that's not true.
If you don't have a 4k TV, the TV will try to down convert the 4k to 1080p, but this is only on a NON 4k TV.
You can also edit your files and then upload to youtube and they will play in 4k on a 4k tv.
When your video is playing on your TV you can use the info button on the remote and it should show the resolution it's playing at.