Hm,
took me a bit before I figured this out. But the search function and "export HumViewer" helped.
Here's what to do:
1. Go to the "File" tab in HumViewer and choose "export"
2. A pop up window opens, asking where to save what type of file.
3. Name the file (i.e. "Battleship BISMARCK" or whatever you've found) and choose "humminbird files (*gpx). Save it under "My_HumminbirdPC in the "GPX_Files" Folder.
4. A pop up window will show asking "what to include in export". Uncheck / Check the apropriate check boxes and hit "OK" (at the bottom of the pop up window). A pop up window will show up saying "data saved successfully".
Now the waypoint is saved in HumminbirdPC.
So far, so good.
5. Next open HumminbirdPC
6. Hit the "open file" icon in the tool bar on top of the HumminbirdPC screen.
7. Hit the File with your waypoint's name.
8. Hit "waypoints". Your waypoint will be shown. Now you can modify it with icons or rename it or whatever (in case it's not the "BISMARCK" you've found).
9. Now you can upload the waypoint either by using your card reader and your SD card or using the ASPC2 connection cable.
Voilá that's it. Hope it helps
Regards / Harry