File Conversion?
Looks like there's 3 options for exporting an image of your map.
In the File Menu:
Export Current Size as PNG Image — The entire map is converted to a PNG image at the default size.
Resize and Export as PNG Image — The entire map is converted to a PNG image after the mapmaker
selects both the desired number of hexagons per inch and the resolution (in DPI) of the image.
Select Area, Resize and Export as PNG Image — After selecting this option, the mapmaker may drag a selection box across the map (and the map may be panned and zoomed) to save a portion of the current map. Both the desired number of hexagons per inch and the resolution (in DPI) may be selected.
The "Game Map" area of RPoL in the GM Menu area accepts PNG files, but they also should be less than 1MB in file size.
I dunno how big your map is, what sort of default resolution Hexographer uses, etc so you may need to experiment with the exporting and resizing to get an image that will work for you.