This is the basic player manual. [We should also link to the Beginner's Guide and Themer's Guide from here as well.]
StepMania 5 can run on this bare minimum:
However, we highly recommend at least these settings for decent performance:
If you're reading this, you've likely already figured out how to install StepMania. Just in case you're reading this without having installed it yourself, however, here are the installation instructions for various operating systems.
The Windows version is available as an .exe installer and a .zip/GameData.smzip combination. The .exe installer is much easier to deal with, but in case it doesn't work out for you, we have provided a zip file for manual installation. The zip distribution can be converted into Portable mode by placing a blank Portable.ini inside of the StepMania install directory.
The Mac version is distributed as a .dmg file; Mount it, make a StepMania folder in Applications/, then put StepMania 5 in there, and make folders as needed. That probably isn't the best way to do it, but it is _A_ way.
Linux users are typically expected to build from source. See Compiling on the StepMania wiki for more information.