The KMZ file is a Garmin Custom Map file and should work fine with your touring.
If you save your KMZ file on your PC (rename it to something.kmz if you prefer) then link up your Garmin to your PC, you should be able to open the Garmin files through the normal explorer. You’re looking for the ‘new files’ folder on the Garmin directory (usually a third of the way down the list). Copy your KMZ file across to that folder then disconnect your Garmin. It should power down but if it doesn’t turn it off and on again. Go into your courses on your Garmin (without connecting back up to your PC) and the new file should be listed for you to pick and follow etc.
If that doesn’t work go to Bikehike and click on the ‘load route’ on the right hand side. Again explore to your saved KMZ file and upload it. The route should then appear on the map. You can then click the ‘save route’ tab, call it something different in the pop up box, and then click ‘download’. Once you’ve done this you can go through the same process as above with your ‘new files’ folder on the Garmin and it should come up.
I’ve given you the second option with Bikehike because sometimes KMZ files that other people have sent me won’t upload, but they always work when I’ve put them through Bikehike.
Hope that works for you.