1. Open your favorite texteditor(BBEdit, Coda, Textmate..) and create a new textfile. At the first line, type the path of the folder where your project resides, e.g./Users/username/myproject
2. Save the file with a .cfg extension to: /Library/Application Support/Macromedia/FlashPlayerTrust/
3. There is no step 3
Note: You can do this for your entire user account, but I strongly recommend not to do so, cos this will allow not trusted files to run both networking and local command on your computer if you download them. You don't want that.