I know I posted how to do this in another thread...
Anyway... you must first click on the dark blue mushroom.
Next open up the new folder called ExGFX.
Then put your custom ExGFX into the folder.
Go back into lunar magic and click on the yellow mushroom.
Find the level you want to use the ExGFX in. Click on the red poison mushroom and in either FG 1 ,2 ,or 3 put the number of the ExGFX into that spot.
The level will then appear broken.Next open up the 16X16 editor. Find a blank page on it ... i.e page 3.
Click on the yellow question mark block with a left arrow and find the Map16 file that came with your ExGFX. Boom!
You now have the Map 16 file in your game but the palette will look odd.
Click on the glowing star and in it use blue star with a left arrow to find the tpl file and just use it.
Don't forget to save the 16X16 editor and then the level.
Finally you can add the level to your doing.