Once your audio is sufficiently screwed, go to File > Export > Export Audio. Try a lot of different things, and remember that Audacity lets you undo things easily and infinitely! At the start, I recommend doing little portions at a time to get a sense of what exactly your edits are affecting.
This is definitely the longest part of the process, since it can take a lot of trial and error for good results. The positioning of the audio data is surprisingly straightforward, so with enough practice, you can approximate what portion you’ll be editing with relative ease. Don’t shy too far from them, though if you avoid them too much, the top and bottom areas of the image will remain unchanged. Try not to edit the very beginning or very end of the audio, as this might end up corrupting the image header, and it won’t be readable as an image anymore. You can also copy and paste portions of the audio data in different places, and even import other audio to play alongside the data. Start messing with the audio! You can use basically anything in Audacity’s effects menu for good results, though I tend to favor Bass and Treble, Echo, Invert, dblue Crusher, and dblue Glitch.