You start off in the Diary (the start page in the app). Click on "+" and choose the type of the meal you want to track (Breakfast, Lunch etc.). On the next page you find the icon for the barcode scanner to the right in the search bar.

Click on the barcode scanner icon, scan a barcode. Done! You can track the item by clicking on "ADD TO DIARY".

In case there is not enough light, please click on the little flash icon in order to activate the light of the phone.