a tutorial here
or you can use Basecamp:it lets you geotag photos — add a photo to any waypoint on the map — so you know exactly what the scenery is like at any given location. You can even transfer the photos to and from your Garmin device.
Please Login or Register to see the links
1) Import photos to PC (eg. Picasa)
2) Connect gps, start BaseCamp
3) In BaseCamp under devices select the gps "All Data" folder
4) Find the track (should be "Current Track" if you didn't save it under another name)
5) Right click it and select "Geotag Photos using track..."
6) Select the folder where the photos are, and follow the prompts.