I followed the guide at www.minecraftforge.net/wiki/Installation/Universal with the forge-1.8-11.14.0.1299-installer.jar and then forge-1.6.4-9.11.1.953-installer.jar install files, but both gave me the message "You need to run the version x.x.x manually at least once."
Maybe there is a miscommunication; You can see minecraft running in this screenshot. Do I need to run something else first? This is my first installation attempt for anything minecraft-related except for minecraft itself. I have no other mods or anything.
Help would be much appreciated!