How to stabilize the oscilloscope signal

First, rotate the "level" trigger level knob to make the "trg led" indicator light up, which means that the trigger conditions at this time are met.

Second, press the "source" trigger source selection button to make the "ch1" or "ch2" mark appear in the lower right corner of the screen. Which one is better depends on which choice has a more stable signal.

Third, press "slope" to trigger the polarity selection button so that a sign similar to "f" appears in the lower right corner of the screen.

Fourth, press "coupling" to trigger the coupling button so that "ac" appears in the lower right corner of the screen.

Fifth, check whether the probe's clip is properly clamped and ensure that the contacts are well connected.