From the Home screen, navigate: Settings > Siri & Search.
If prompted, tap Enable Siri.
Tap the Listen for 'Hey Siri' switch to turn on or off .
Tap the Press Home for Siri switch to turn on or off.
Tap the individual apps you want to use Siri with then tap the Siri & Search Suggestions switch to turn on or off .
This will allow your info (e.g., location, nicknames, things you say, etc.) to be transmitted to Apple so you can use Siri within certain apps.