Need help with SM on Mac! unable to add songs

[DDR_M45T4]

I have a huge problem, I havent owned a computer in a while and I finally got an old 2008 macbook from someone for free. the only thing I really want to do is get in stepmania again, but when I downloaded the game for mac (It runs, I tested it) I am not able to add anything to the files or make any changes.
I know how to add songs to the game so that isnt the issue, its that the stepmania files wont give me "permission" to do anything except look at the files, and I cannot add songs and play the game if I can only read its contents.
I tried everything, I went to the options by right clicking and changed the "permissions" by unlocking the lock icon and entering my admin password, but that did nothing. I still cannot add anything to the files.
if someone could please help me out that would be great! FFR is the only place I think Id get answers