You can tap the barcode symbol or shake your phone (enable in Menu -> Settings -> Shake to Open Camera) to launch the phone’s camera to capture a barcode. However, the camera is much slower than using a Bluetooth scanner and will use more battery power. Please see the video below for a demonstration:
Enable/disable Quick Scan
It would help if you allowed Scoutly to use the iPhone’s camera by tapping Settings -> Privacy -> Camera and making sure Scoutly is enabled.