If you're using Upload Studio on the Xbox One, it's very easy to record a voice over on your clips. When you boot up Upload Manager, select "Manage your clips" and select the clip as desired, and go back to the left where it will say "Edit in Upload Studio".
On this screen, you will see your clip on the right hand side, along with options on the left such as Change Type, Change Effect and Trim. Below that you will see "GAME DVR" which will have been your clip. In order to do a recording, you will need to plug
in a chat headset, or use the stereo headset adapter before the "Add Voice-Over" option will be highlighted and available for use. It's probably more than likely possible to use the Kinectmfor recording too, but I can't vouch for that since I don't own one.
Once you have hit record, your clip will play alongside as you record. Once you're done with the recording, either let it run, or stop the recording.
To preview what you have recorded with the microphone, simply press the X button to preview the clip with whatever you have recorded alongside it.
If you are unhappy with what you have recorded, simply choose "Clear Voice-Over" and you can start fresh.