If you want to keep it HD, and use your Xbox One for playback, you’ll need to make a properly formatted Blu-ray or AVCHD disc.

Load the MKV into tsMuxeR and have it build you a Blu-ray or AVCHD folder, then burn that to a disc (BD-R or DL DVD-R respectively) with ImgBurn.

If you want to use your DVD player (and it doesn’t have MKV or AVCHD support) you’ll need to completely rebuild each film as a standard def DVD. Last I checked, ConvertXtoDVD was a decent all-in-one tool for doing that.