Help getting file from Shortcut

Hi! I just got my iPad yesterday, so I'm a bit new to the Shortcuts app as well as a-shell.

My end goal is to convert an audio recording into a video with a solid background. I've been able to automate this in a batch script on Windows, but I'd like to be able to do it directly from my iPad as I'll be using the voice memo device. This is the command I use in the batch script.
`ffmpeg -i %infile% -f lavfi -i color=c=black:s=640x480:r=15 -acodec copy -shortest %outfile%`

At this point I can't even figure out how to pass my audio file on my iPad to Shortcuts and then a-shell. I've tried a few things like passing from share sheet or using the get file, but these don't seem to work or I'm not using them correctly. 😅

Can you please advise? 😁