You can use Garmin Express™ software to download and install the latest map and software updates for your device. Map updates provide the latest available mapping data to ensure your device continues to calculate accurate and efficient routes to your destinations.
This wikiHow guide shows you how to update your Garmin Nuvi using a Windows or Mac computer. You can update the Garmin Nuvi the official way by downloading and using a free program called Garmin Express, or you can install community-created maps from an unaffiliated 3rd-party website.
Subscribed 291 69K views 5 years ago Updating maps free on a Garmin GPS using OpenStreetMap part 1...more
This blog post is about how to install free maps on a Garmin Nüvi 255W Sat Nav. A friend purchased an old sat nav via eBay and asked me to replace its 2010 UK map with a more recent map, as well as install a free map for Australia. I found an excellent site that provides free maps.
To ensure that your Garmin has the most up-to-date software upgrades and maps, use the Garmin WebUpdater utility. The WebUpdater application automatically searches for upgrades and additional maps for your device, downloads the necessary files and installs them directly to your unit for free.