First you need to look at the On Application Start event trigger, then choose Play Action Sequence. Now select your animation on the stage, then select the Timeline panel. Click the Add Action button. You can then select the Play menu choice to play your animation.
However, I would HIGHLY recomment that you do not use Flash Catalyst in this manner. The product has been discontinued by Adobe, so you issues with your projects at some later date. Also, the project will not work on any iOS device or any newer Android device. I would recommend that you look at using web standards for your project. If the animation is complex, look at Toolkit for Create.js extenstion for Flash to convert your Flash animation to a HTML5 based version. Or you could look at Edge Animate to rebuild your animation.
Good luck,
Chris Griffith