Pick any character in World Tour mode. After you clear 19 courses, and reached level 27, clear the USA course that opens up. Guile will be your final boss. Beat him, and you'll be able to use him in any mode. Ok, that makes it sound a little confusing than it actually is, so let me explain. In SFA3, you get experience points assigned for each fight, raising your characters level. So what you need to do is concentrate on getting perfects and doing super moves, as those give you the most experience. Your character needs to be level 27 by the time you reach M. Bison as the final boss. (M. Bison American, Vega Japanese) If you have, after you beat him, a new location will open up in the USA. You will go there, and get to fight Guile. Beat him, and he will be playable in any mode. If you just can't seem to do that, he is unlocked automatically after 96 hours of play.