how to integrate external audio to a video?

[esteban]

hello,my name is esteban and my question is: how to integrate external audio to a video permanently with bs player?
i was using the program atube catcher to capture a video online (stream catcher option), and I could download, I elected mp4 video format but the problem is downloaded audio and video separately.
researching on the web I found that I could integrate my video the audio separately from video (external audio file) with the options: menu + load external audio file, so it works perfectly the video MP4 with audio but when you end the reproduction the video and restarting again or close the video and then I open it I have no sound (video only)
as I can do to integrate video and audio permanently?
thank you for your time and appreciate even more answers