Difficult to find any instructions on how to use this anywhere.
Didn't work when it arrived so dug around and eventually found 'reboot' which got the BPM working. It just kept saying 'tighten strap' when it was already strangling my wrist! Not sure what I did but eventually the step counter started working too. Happy with it now but you really have to play around in the app and on the the tracker to sort it all out.