Forge and Optifine

[JJMACCA]

I'm trying to add forge and optifine together in the modpack.jar file and when I launch it closes and the log says forge found a different class than what was expected so optifine is overiding the forge files. How do I fix this and does it have anything to do with the fact that I didn't really know where to get the optifine files from cause when you download it it gives you a installer so I just opened it with winrar and took the files that wernt in a folder.

Thanks