Couple of software recommendations:
It is definitely advantageous to learn the basics of video editing software that supports multiple tracks (audio sources, video files, etc)
In my own journey I started with the free iMovie and/or windows movie maker: taking the ipad (or other camera) video file and lining up the audio from hauptwerk (the recorded .wav) file manually (eyeball technique) and then 'muting' the audio from the camera so that all audio comes only from the hauptwerk recorder.
The 'fancier' video software can do this automatically.
Cyberlink Power Director is a windows application that allows you to "synchronize audio" between multiple camera angles (or just your single camera angle and the wav file) and then you can mute the camera audio
I am now learning how to use adobe Premiere and it also has a 'synchronize audio' feature - import all the sources into a time-line and then the system lines it up for you.
I did a quick youtube search to find some directions on this, and this tutorial outlines using a free software package to do this. - this is the concept you are looking for
https://www.youtube.com/watch?v=9HbuASf8k6w