Press the test button.

The test button is usually coloured. If it is not, it is usually the only button or labelled "T" or "Test".

Contact an electrician to replace your RCD, if this did not cause your RCD to trigger!

To turn your power back on, you'll need to flip the lever back up, or press the reset button.

The reset button is usually the only other button on the device or is labelled "Reset".