There are two ways to add a new trigger - by creating a new scene (that will appear on the trigger when its scanned), or by replacing an existing trigger.
Navigate to the 'scene list' view by clicking 'scenes' in the navigation bar. Click 'Create New' to make a new scene, and you will be asked to either use a generated marker, or add one you have prepared.
Click 'Upload' and select the image file you want to use as a trigger (the image file must be a JPEG/PNG file). See 'What makes a good trigger' for details on how to choose the best kinds of trigger.
You will then be taken to the scene editor for that trigger. You can see the trigger on the right hand panel (alongside the scene name and other tracking settings like extended tracking). Now when someone scans your image, this scene will appear.
Please note it may take up to 2 minutes for your trigger to become active in your app, and you may need to restart your app to recognise the new trigger.
To replace an existing scene trigger, see 'How do I replace a trigger'.