You can always turn your lights on or off via the wall switch. Or if you’re using free standing lights, just plug them in to switch them on. Or add a Hue Tap or Hue Dimmer switch to your system and you can control your lights without the app. Or to control them automatically, install a Hue motion sensor.
You can also control your lights through the hue website (www.meethue.com). Just make sure you’ve enabled remote access.