how can move the robot using the keyboard

[downloadproject]

https://gazebosim.org/docs/harmonic/moving_robot/
This webpage tells me how to use the keyboard to control the robot's movement. But when I used this code in your project, the robot stopped displaying. Where should I add this code？

    <plugin filename="gz-sim-triggered-publisher-system"
            name="gz::sim::systems::TriggeredPublisher">
        <input type="gz.msgs.Int32" topic="/keyboard/keypress">
            <match field="data">16777234</match>
        </input>
        <output type="gz.msgs.Twist" topic="/cmd_vel">
            linear: {x: 0.0}, angular: {z: 0.5}
        </output>
    </plugin>