Der Versteckfinder

I've loaded gsak, set up my garmin gps and tried to download a geocache site to my Garman. GSAK displays a green moving line followed immediately by a moving red one and then the window closes with no error messages or any indication that anything is wrong. There is nothing being sent to my Garmin. Do I need any Garmin software on my PC? How can I get GSAK to send data? I just started trying to use GSAK and I'm probably doing something wrong, but I can't figure out what. Any suggestions?