Make sure your heart rate monitor or bluetooth headphones are in pairing mode, usually there is a blue light that will flash to indicate they are in pairing mode.
Also make sure they are not connected to the bluetooth settings of your app and only connecting via the bluetooth in the app. Then simply tap the broken heart icon or headphones icon on screen (for EX5S) and it will pair. If you have a chest heart rate monitor from Echelon, make sure it is soaking wet, this is how to put it into pairing mode.