well, besides some unofficial products that make swfs (all inferior) you need macromedia flash.
you can try it out here with a 30 day free trial.
you will also need a computer with windows, or a mac. there is no decent flash maker for linux, saddly :(
hope that helps :0
aside from making flash. There's audacity which allows you to cut up song.
and things you should search up are sprite sheets, unless your drawing something yourself then forget that
you should also search up roms as you can use those to get sound effects
and for music, I would with newgrounds' audio portal has great ones. Another site that I would use is vgmix.com. You should also use some real songs some of those are good to use.
