I assume you are talking about the app on your phone.

If so, there are two cases in which you could access the RK. One, if your phone is connected to your wifi, you can use the private internal IP of the RK to access the device. If your phone is NOT on your wifi, you need to setup NAT in order for your router to know to forward the traffic to the RK from an external port. You will need your public WAN IP for you home network in order to accomplish this.