To capture Flash on OS X with the Flash Decompiler Mac, please refer to the following steps:
1. Install Sothink SWF Catcher for Safari to your computer at first.
2. Open the webpage that contains the Flash you want with Safari.
3. Go to menu bar of the browser and click "SWFCacther > Run SWFCatcher" button.
4. Choose the save path for the Flash file and click "Save" in the next pop-up window.
5. Click "Open with SWF Decompiler" button and decompile the Flash with the Flash OS X Decompiler at last.
P.S. For detailed instrctions, we suggest you refer to the tutuorials below: