To launch Siri, press and hold the home button. In other words, the big round button under the screen. Your mobile device must be on, but not necessarily unlocked. When you hear two beeps, you can release the button: a microphone icon appears on the screen, followed by the text "what can I do for you?" ". Siri is activated! Do you have your hands free and the hesitant gesture? Click the question mark in the bottom left of your iPhone for examples of tasks Siri performs.