Take your source image and your counter
Make sure both are RGB (the counters start as indexed).
rescale your source image to 14 pixels by 9 (14x9), copy it and paste it into your counter and move it into the black box.
You can do the same for the roundel - get a source and place it within the grey box (some counters do not have the box, but the grey box defines the limits that the roundel will be read).
Then 'save as' your tag and bitmap extention.
you should now have a 6.42kb counter where your program is (i.e. save it there)
left click on the counter and the prototype counter (holding down the 'Ctrl' key to select both) and drag both over the program exe file.
you should now have a 3.17kb 'counter_NEW.bmp': this is the counter you use in the game.
Delete the old one (CSA in this instance), rename your NEW counter to your tag, replace the one in the GFX/palette folder of your HoI2 directory (back it up first of course) and enjoy.
Aye.