Long-clicking an active sensor display brings-up sensor information. "Forget" deletes that sensor from your database.
Long-clicking an inactive sensor display brings-up a Search & Pair list of appropriate sensors. A green icon means the sensor is already in your database. A red icon means that is an unknown sensor. select the sensor you want to connect.
Only one app can connect to a Bluetooth sensor. If CycleBike Smart doesn't connect, maybe the sensor is paired to something else.