The Arduino IDE provides a sample sketch with a simple program outline in a text window when you first open it. There are also a vast array of code samples under the File->Examples submenu item.

If you are interested in learning more about using the Arduino Nano 33 BLE ... you just want to use it as an Arduino; setup() and loop() ... with a cornerstone of Arduino: open-source software.

The software uses proportional and integral control (the PI part of a PID loop). Although the Arduino has a good selection of I/O pins, it doesn’t have common I/O capabilities you’d expect in ...