Plug the 4G modem into the USB port on the back of the Boost, under the weatherproof flap.
Connect the Mevo app to the camera, then go to Settings. You will see the 4G/LTE Modem status appear on the top panel, next to the battery indicators, storage information, and Disconnect button. Please note it may take up to a minute for the connection to be detected in the app.
If you go into Network, you should see that LTE Modem + Mevo Hotspot has appeared as an option.