If you are like me and bought an Android phone that is not compatible with the G6 app you can get it off Reddit for any phone. Go to: https://www.reddit.com/r/diabetes/comments/8ja38m/oc_build_your_own_dexcom_app_now_with_g6_support/
You can also download Xdrip+ in place of the G6 app and you can also use Xdrip+ for Follow App if your phone isn't compatible. I use Follow and Xdrip+ to follow my 5 year old because it gives much better predictions and it alerts me sooner for lows. Get Xdrip+: https://github.com/NightscoutFoundation/xDrip. To use Xdrip+ for Follow you do not need a nightscout website to use it. You can use Dexcom data source.