If you want Siri to respond, you have a few options. Assuming you have Hey Siri turned on (as explained above), you can say "Hey, Siri." If this option is not turned on, there are various ways to wake her up. This all depends on the device you're using. If your iOS devices has a home button at the bottom of the screen, long-press it to wake Siri up. If your device does not have a home button, press and hold the button on the right side of your device (formerly the power button). If you're using a Mac, you can use click on the Siri icon in the menu bar (located in the very top right-hand corner), you can use 'Hey Siri' (if enabled in the System Preferences), or you can set a keyboard shortcut to activate the virtual assistant.