Earl’s Github page is a good place to start, and on there is a link to the docs which might be helpful? There is a section on multicore processing.
Although I have a couple of Picos, I haven done anything with them other than to blink the LED using the C/C++ SDK.
In case it’s useful, all the Pico and RP2040 docs are online and probably contains more info than we’ll ever need!
HTH
Cheers,
Norm.