Here are the players:

    Garmin Explore Website – This is where you register your InReach, setup contacts and messages, and optionally use the mapping software.
    Garmin Explore Smartphone App – With the app you sync the device to the phone using Bluetooth, and then you can transfer the InReach settings from the website to the phone. You can also use the basic tools to create tracks, routes, or waypoints, and then transfer them to your phone. Lastly, the smartphone app works as a controller for the Montana when it’s connected via Bluetooth, allowing you to “remote control” many of the Montana’s features.
    Garmin Express – This is a program that you install on a computer to update the firmware and maps on the Montana. You need to connect the Montana to a computer using USB to use Garmin Express.
    Garmin Connect – Yet another app for your smartphone. Before you can connect the Garmin Explore app, you need to connect with Garmin Connect. Why? Who knows? It makes no sense.

Here’s how to do it.

If you don’t want to activate InReach or have a Montana 700, skip to step 7.

    Turn on your Montana and go through the guided setup.
    You will get an IEMI and activation number, write those down.
    Go to the Garmin Explore website and sign up for an account. You will use these same credentials to log into all the Garmin apps and services in the following steps.
    Enter your IEMI and activation code, pick a plan, and put your billing info in.
    Go back to the Montana and and continue. The Montana will send a message to the Iridium satellites and then get one back with a successful activation.
    Go to Garmin Explore website and enter your contacts and preset messages.
    Load the Garmin Connect and Garmin Explore apps on your phone. Turn on Bluetooth on your phone. Go to the settings on the Montana and add a new phone.
    Open Garmin Connect and add a new device. Select the Montana. Let them pair.
    Once paired, open Garmin Explore on your phone and add a device. This will sync your InReach contacts and messages, as well as any saved navigation data. Almost there…
    Install Garmin Express on your computer and connect your Montana to the computer with the USB cable.
    Add the Montana to Garmin Express and sign in with the account you created for Garmin Explore in step 3.
    Update the firmware and map data. And that’s it, only 12 steps!

I highly recommend downloading and using the Garmin Basecamp program for your computer. It’s a good planning tool that’s integrated with the Montana.