Get yourself up and running quickly, use the guide below to enable Siri on your iPhone.
If you choose to restore your device from an iTunes backup or from iCloud, you may find that Siri is turned off once the process is complete. If so, follow these instructions.
iPhone 4s or later.
An Internet connection (wireless or 4G upwards is best).
Setting up Siri on iOS:
Navigate to Settings > Siri & Search.
Make sure Press Side Button for Siri is toggled on.
Choose your language, your voice feedback preferences and make sure your contact details are selected in My Information. (This is so that Siri knows who you are and can begin creating ‘relationships’ such as ‘wife’ or ‘brother’ with other contacts in your address book).
Switch on Listen for 'Hey Siri' if you wish to activate Siri using your voice, without pressing the Side/Home button.
Switch on both Siri Suggestions options. These options enable a screen that shows your most used apps and the people you've recently called or messaged.