Choose intern as the trigger mode, the channel you are using as the trigger source, and the trigger conditions are usually "rising edge" ("falling edge", "burr", etc.).

Finally, adjust the trigger level. If there is a trigger level scale, please adjust the scale to the range of measuring signal amplitude.

The setting keys of different models of oscilloscopes may be slightly different, which is roughly the case. If it is a digital oscilloscope, the waveform will generally be stable if it is set automatically.