I don't have a clue how to make music, are we allowed to use 3rd party music that's available for free?
You're welcome. As a last resort you could try to use (Wolfram Tones)[ http://tones.wolfram.com ], which I sometimes use if I need something closer to an 'ambient' soundscape. (Like this time.)
How I don't know much about music either, and I've used [ https://www.beepbox.co ]. Learned of it's existance during a jam, and immediately used it even! Other people are great fans of [ https://boscaceoil.net/ ], which is sorta similar. You can do post-processing with [ https://www.audacityteam.org/ ].
Use of pre-existing: Not in the ranked (solo or team) versions: From the (rules)[ https://alakajam.com/article/alakajam-competition-rules ]:
You must make all your audio assets during the event. However, you are allowed to use:
Any existing sounds for SFX or as short samples for music, including drums and other sampled instruments (reusing full music tracks is not allowed);
Assets created from sound generation or speech synthesis tools.