File -> Build Game
In there go to the 2nd tab
Select the 2nd script in that new window.
In there you will find the path to the skymaps, there you can change them.
This is how you change them, to actually place new ones, you just need to trow them in the same folder the other ones are (you can put them on other folders, but if everything is in the correct defaault folder, it will help you later locate them), then, of course, change from the default one to the new one, for easy checking which folder the skymaps are, go the the same tab i told you, wince it shows the direct location of the skymaps.
My love is seperated in 2 parts, 1 of them is 3ds Max 7, the other; FPSC.