You need a Retial version of Windows 7. Home or Pro doesn't really matter unless it it matters to you personally.
And basically that's it. You use Boot Camp Assistant to partitioin the drive and then install Windows 7.
Or you could use one of the Virtual Machine software programs and install any version of Windows in a virtual machine. So for that you would need the VM software and a version of Windows.
Or you could go out and for a few dollars more buy a Real Windows computer with Windows 7 Preinstalled.