Then click the 'Open' button in that window to launch the installer. If so, click the 'Open Anyway' button which will display another window. Most likely because you tried and failed opening the installer by double clicking without holding down the control key. It should inform you installation was successfull. Note that the Soundflower extension is signed, but the installer is not! You will have to hold the control key down to open the Soundflower.
