Pairing heart rate sensors directly to Seconds is no longer our preferred way of acquiring your heart rate.
If you are using an iPhone should pair the heart rate sensor directly with the device and let it write your heart rate data to Apple Health. Seconds will then read it from there.
If you use an iPad pairing the sensor directly with Seconds is the only option.
While wearing your heart rate sensor and tap Discover Nearby Sensors. Select your sensor once it appears in the list.
To view the heart rate during a workout you will also need to configure your timer display.
You can see these settings being applied in the screencast below.
Either swipe left along the row in My Sensors and hit the Delete button, or tap Edit from the navigation bar, tap the Delete Icon and then tap the Delete button.
Some users have reported problems pairing their sensors if they have previously paired the sensor within the Apple settings. In this situation you will need to unpair the sensor before trying again within Seconds.