I was at a loud convention and the audio from my camera was super loud and screechy, how do I fix that?

If its loud and screechy it means the audio is overloaded and usually that cannot be fixed.

Next time set your camera audio to manually to you can manage the levels.

Might want to try the trial of Audition; it has lots of tools and features.

The hardest thing to fix in video production is audio.

There are "Audio Effects" in the Effects tools section.  They can't make it perfect, but may help depending on where the screeches are.   There are well done YouTubes for how to use the Audio Effects.

Outside of Premiere Elements is the (free) program Audacity.  It may do more for your audio than Premiere Elements.