Learning How to update Garmin express is straightforward. Before starting the update, make sure your Garmin GPS device is connected to a computer. Using a micro USB cable, connect the GPS to your computer. If you've already connected the device, the questions should start popping up right away. Download the software for Windows or Mac. After you've downloaded the required file, click the update button and continue the on-screen instructions. It's now time to put your newfound knowledge into practice.