If Audacity is running, do Audacity > Quit Audacity.
If Audacity does not quit, do COMMAND + Option + ESC. In the Force Quit window that appears, select Audacity then click Force Quit.
Then Trash the Audacity folder(s) you copied. Then see here for how to install Audacity properly: Installation: Do NOT run Audacity from the DMG!!!!
Gale