The program's name is now SAP PowerDesigner and it hasn't been developed to run on the Mac OSX operating system which means that you won't have the possibility to install it on that operating system.
The only way to do it is to install one of the versions of Windows supported by PowerDesigner using virtualization, and by virtualization I mean Paralells Desktop.
Currently the Sybase PowerDesigner is compatible with: Windows Client 32-bit, 64-bit, Windows for IA64, X86, X86_64