Your entry will register with the location on maps during the upload process using the image's EXIF data.
However, if your entry doesn't have the appropriate EXIF data for location, then you can manually do this yourself during the upload process by ticking the "Add to Map" box. A new map window will open with a search field to zoom in to a specific area.
You should then select the appropriate spot on the map where you took the shot. Simply plot your location with a pin and then click the 'X' to close the map.