I have done it this way.
While recording in Cubase, also record the video with sound (I use my cell phone).
Then, when I am done mixing all the different audio parts in Cubase, I export the final audio track.
Then, I use a separate video editor (Vegas Pro) and import the final audio track and all the video files.
To sync them up, I turn on the sound of the video files and use that to nudge the video files into sync with the final audio file.
I find it helpful to pan the video audio to the right and the final mix audio (from Cubase) to the left.
Then, turn off the sound from the video files and center the final audio.
You may not be able to record the video into the computer with the audio. It may be too demanding and cause audio dropouts. Plus, I have found that My phone actually has the best HD video recording of anything else I have tried (including a Sony HD Camcorder!).