Indoor bike not recording distance

How do you get the distance from the bike to the watch? Which sensor are you using?

I go to  a spinning class a few times a week and garmin watch normally links to the bike I am using. Since internet upgrade not linking to bike for stats..

Thanks Andy, that solved the problem. 

BTW, if you use a bike in a gym, you either have to use the very same bike each time, or to remove and add it (as e7andy advised) every time you go there. If you do not remove the bike of the last spinning class, and ride another one, your watch will read the distance from the neighbor using your original bike.

Thank you