The following steps need to be followed to use a pH meter:

1. Preparation: Insert the pH electrode and reference electrode into the container of the measuring solution, making sure that the electrodes are in the liquid. Usually, the electrodes need to be calibrated and cleaned according to the instructions in the pH meter manual.

2. Power on: Turn on the power of the pH meter and wait for the instrument to warm up.

3. Operation: Immerse the electrode of the pH meter in the solution to be tested and wait for the electrode reading to stabilize. According to the experimental needs, the measurement mode of the pH meter can be set in advance, such as continuous measurement, single measurement, etc.

4. Reading: Observe the display of the pH meter and record the displayed number as the pH value of the solution according to the instructions in the instrument manual.

5. Shutdown: After use, shut down according to the process in the pH meter manual, and clean and store the electrodes.

It should be noted that the pH meter should be used with caution, especially when testing in high-concentration, toxic or volatile liquids, to ensure the safety and accuracy of the experiment.