How to install Optifine? Using the Forge way isn't working, and the.jar file isn't opening

Uhmm i think google it

I never use programs like that. Try doing it manually. Install a clean version of the free program 7zip, then open the minecraft.jar file in that and transfer the OptiFine folders in there manually. Just move it into the jar. Then delete the META-INF folder, and you should be good to go. Make sure you follow any specific instructions on the mincraftforums official post.