If you have not used this tracking service before, please register - enter your email address and an access code which you should keep private, and select your timezone / region. Then click on "Join up".
If you have used it before - and want to re-use the same info - please just enter your email address and the same access code as before, and click on "Rejoin". No need to set the timezone info. Note - you'll need to do this on each device / browser so they can all share the info without anyone else being able to see it or change it.