Go to Settings -> Sensors & Accessories and <Add New> It should find and pair with your sensor in ANT+ mode first and then BLE mode. Afterwards you'll find your sensor in the list twice - once for ANT+ and once for bluetooth (the names aren't always obvious but it shouldn't be too hard to work out which is which). If you don't ever want to connect via bluetooth you can select the BLE device name and change the status to off.
