You can accomplish this by adding an Interaction to your project, with the definitions of "On Click" and "Go to URL". There is brief info on this in Help, refer to the graphic here: http://help.adobe.com/en_US/flashcatalyst/cs/using/WS4bebcd66a74275c3-326fcb52123816c0204- 7ff0.html. If you prefer a more visual tutorial, check out this video at about the 3:15 mark: http://tv.adobe.com/watch/learn-flash-catalyst-cs5/gs04-adding-interaction/.
Hope that helps!
Thanks for the answer, but I want to put the actual video on the pageand not just the link
You can't do this directly in Flash Catalyst, though I believe you can do it in Flash Builder. Here's an older post that covers one way of doing it: http://forums.adobe.com/message/2031783; you can probably find more recent info and other alternatives by searching, depending on what software you're comfortable with.
If you have access to the source files for the YouTube video, you can import that into Flash Catalyst (Catalyst supports import of FLV and F4V files). Here are some links that explain how: