Find a note "C" on the piano. "C" is the white note immediately to the left of each pair of black notes.
Find the "C" note that is closest to the center of the piano keyboard, looking from left to right. This is "middle C."
Place your right thumb on "middle C" but do not press down on the key.
Place your right index finger on the white note directly to the right of middle C. Again, just keep your finger on the surface of the key. Do not press it down.
Place your right middle finger on the white note directly to the right of the key where your index finger is resting. Again, just keep your finger on the surface of the key. Do not press it down.
Place your right ring finger on the white note directly to the right of the key your middle finger is resting on. Again, just keep your finger on the surface of the key. Do not press it down.
Place your right little (pinky) finger on the white note directly to the right of the key your ring finger is resting on. Again, just keep your finger on the surface of the key. Do not press it down.
Press down the five keys with your five right fingers simultaneously. Voila, you have just played a diatonic cluster chord.