The Microsoft Surface 3 is a tablet running Windows 10 so installing wearable devices like the Garmin vivosmart HR is different from what you may be used to on Android or iPad tablets.
If you go to the Microsoft App Store and look for the Garmin Mobile Connect App you won't find anything.
Instead, you need to go to Garmin's website at http://connect.garmin.com and click on Get Started.
From here, you can select the vivosmart HR at the bottom of the page for more step by step instructions.
Once you are in the vivosmart HR instructions page, first select Computer rather than Mobile.
Make sure your vivosmart HR is powered on, attach the USB cable to the back, and connect it to the Surface's USB port. After you plug in the cable, you will see a message that it has enumerated as a drive (which you can ignore).
Next you need to select Download for Windows.
After the download has completed, select Run and Garmin Express will get installed. Garmin Express is the main program that is used to sync your Surface with the vivosmart HR.
You can then launch Garmin Express and select Add a Device. The vivosmart HR should be found automatically.
After your vivosmart HR has been connected, you need to either sign in with your Garmin account or create a new one.
Once you are signed in, you can continue customizing your profile and settings.
From here you can start exploring your fitness data. There isn't a special App to use for this- everything is done through your favorite web browser. There is a wealth of vibrant colored graphs that you can use to monitor your steps, calories consumer, heart rate, sleep patterns, etc.
If you go directly again to http://connect.garmin.com you will start with a helpful tour of the site.
Garmin Connect also has a nice magazine-like way to scroll through a summary of all your fitness data.
Unlike other tablets, it's easiest to sync your Garmin vivosmart HR with the Microsoft Surface 3 using USB rather than Bluetooth. Of course, this means you need to carry the USB adapter around but one nice benefit of using this adapter is that you can start charging your vivosmart HR while you sync.
The web browser of Garmin Connect is also a nice complement to the Android and iPhone/iPad Garmin Mobile Connect App, allowing you go through a lot more data in a comfortable less space constrained environment.