Basically, just press the button. You have 1 second. Press space to start. If it doesn't work, press green flag until it works.
I got the idea from cps test org. CPS stands for clicks per second btw. Also if it does not go back to 0 in 1 second, press the green flag twice. Update list: v1.0: added basics. v1.1: added auto clicker detector. v1.2: added extra details. v1.3: added world record. v1.4: added small changes.
