Load Humminbird PC on to your computer from the Humminbird Website (free).
Download All your waypoints onto a SD card. Upload the contents of the SD card onto your computer. Review you waypoints in HB PC. Review and Edit the waypoints (delete etc).
Clear the SD card and Humminbird Head Unit. Copy the save waypoints back onto the SD card. Upload the modified SD card data back onto the the head unit.
Take your time, look at the waypoint in Google Earth. Have fun. Sound more complicated than it is.