StepMania does not currently run on macOS 10.15 "Catalina". 

Install Stepmania. Got a .DLL Error? Watch this youtube video:

Go to Stepmania website.

Click on either Windows or Mac. (NOT CATALINA!)

Install the software (run or save)

Click on the software Icon.

 

WINDOWS

If you get an error message - check it. If it mentions  DLL file. Then follow this youtube link.

https://www.youtube.com/watch?time_continue=1&v=c5fxzdD3tZA&feature=emb_logo

MAC

If you get an error message about note skins follow this thread

https://github.com/stepmania/stepmania/issues/1299