The simplest thing to do is as follows: Go to the following website-
Follow the instructions from there which state:
WebUpdater is a free application that lets you update your unit software from home. Download it once at the link below, and you can check for and install software updates without using your Internet web browser. Simply run WebUpdater from your computer, and it will do all of the work for you.
Step 1: Download and Install WebUpdater
Click the link above to download WebUpdater. Next follow the screen prompts to install the application on your pc. If you have already installed WebUpdater on your computer, skip to step 2.
WebUpdater updates most Garmin products, excluding Palm and Pocket PC devices, fixed-mount marine units, chartplotters, fishfinders and certain discontinued units we no longer support. It does not perform Beta updates. WebUpdater only updates unit software. See our All Updates & Downloads
web page for related utilities, drivers, add-ons and the unit software for the excluded units mentioned above.
Step 2: Connect GPS to PC and Run WebUpdater
After installing WebUpdater once from the Garmin website, perform all future software updates from your computer. Simply connect your compatible Garmin device to your computer, then run WebUpdater from your computer's "Start Menu" by selecting "Start", "Programs", "Garmin", and finally "WebUpdater".
Hope this helps.