CFS3 only recognizes two seasons as far as terrain textures are concerned - spring/summer and autumn/winter. WOFF gets around this by swapping different seasonal textures in and out of the game directory based on player choices. Without a WOFF manager for CFS3 you have to do this manually when you want change seasons. The other option is to download Winding Man's scenery manager (it's the WOFF manager's great great granddaddy) from here and you can then make your seasonal selections using that program. After installing the scenery manager, you can replace the seasonal textures it comes with with the ones from WOFF.