Hello,
Start here:
I found this useful once I was comfortable with Processing:
https://natureofcode.com
This inspired me when I was younger (and still does!) and available now for everyone:
See examples available with Processing:
This was a project I started with an object file:
More examples:
Work through examples and start thinking about what you can do with the palette of tools that Processing offers!
Its math, programming, inspiration, and creativity combined.
A worthy pursuit.
Some “rough cuts” of projects I posted on YouTube: