Hi Tom,
Welcome to our community!
To broadcast the internet to your Reach RS+ via your phone’s mobile hotspot, you should first connect your receiver’s hotspot. Then, check your phone’s hotspot credentials and set it up in Emlid Flow. This guide will help you with this.
If you’d like to stick to the Bluetooth connection, you can use it as well. In this forum thread you will find detailed information about it, but please note that it’s in Beta for now.