How to upload from Garmin Edge and Forerunner Devices
If you have a Garmin Edge 500 and are running windows, you'll
want to use our ride file uploader. Go here
http://support.strava.com/faqs/upload/how-can-i-upload-ride-files-t...
If you are already a Garmin Connect user or know that you have the Garmin Plugin installed on your web browser, all you need to do is plug in your device to the USB port on your computer, click the "Upload" link on Strava, and away you go.
If you are new to Garmins and uploading from them, this FAQ post gives you some resources to help you get started.
Getting Started on Strava for Mac Users:
http://blog.strava.com/2009/06/15/strava-on-a-mac/
Getting Started on Strava for PC Users:
http://blog.strava.com/2009/06/11/strava-on-a-pc/