You can do the whole thing without the fitness band so let it not stop you

All you need to do to register at nationalbikechallenge.org and then just type in your miles every day or every week ...
You can also choose to use a phone app like MapMyRide and then link it to the bikechallenge or a fitness band
The fitness band, hopefully, makes it simpler. It records the miles and it all gets synced and updated on the web site.