Pico doesn’t have a reset button on board and the tutorials start off as running the code by pressing the “run” button the thonny IDE.
To add a reset button please follow this post . It says to add push switch with one lead to Pin 30 – RUN pin and the other lead to ground.
To run a code on boot, rename the code as main.py and save it on the Pico and it will run on boot independent of the computer/IDE.