A:Answer If you have recorded the sound into audio files such as mp3, Photoshop Premier Elements should do the job. I suggest the 2018 version. This can handled mixing several audio files / tracks with video and still images.
If you are asking how to record and mix realtime audio you will need sound mixer software. Audacity is free on the internet. Just Google it. If you want something more sophisticated, check out the music mixing software offered by Best Buy or search online.