From the documentation:
Run the setup application and follow the instructions in the installation screens. (In your case, mount the .dmg and follow the instructions to install it).
Start the simulator: open the folder where you installed the simulator, and double-click BlackBerry10Simulator-BB10_n_nn, or BlackBerryPlayBookSimulator-n.n.n.
You may also encounter Java issues installing, in which case you'll need to install http://support.apple.com/kb/DL1572