To transfer tracks to your GPS a Garmin program is required, depending on your GPS model the program is called either Garmin Mapsource or Garmin Basecamp. If you don’t have this you will need to get hold of a copy from somewhere.
Download the files for the tracks you want from the site. Depending on the capabilities of your particular GPS model your GPS may accept tracks with 50 navigation points per track, or up to 250 points per track. You will need to do your own research on your GPS model to ascertain this. On each track page you are interested in click the ‘Download a 50 point GPX trackfile’ or ‘Download a 250 point GPX trackfile’ link as required and a popup window will appear asking where you want to save the file on your computer. Save the file to your computer in a location that you can easily access.
Once thats done you need to ensure your GPS is attached to your computer via USB cable and start the Mapsource or Basecamp program, whichever you have for your GPS. In Mapsource or Basecamp open the GPS file(s) you want to transfer, once open there should be a menu option at the top of the screen to transfer them to your GPS.
If you have the Garmin Mapsource software this video gives you a quick walk through.
If you have the Garmin Basecamp software this video gives you a quick walk through