where does the PHP code go?

I’ve installed the CG Dynamic Sidebar plugin and activated it. I’m on the Widgets screen. I’ve added a new sidebar area and added a widget to it.

Now what do I do? There is PHP code – where does that go?

I want to have one Right Sidebar for some posts and a DIFFERENT right sidebar for other posts. Will this plugin do this? If not, is there a plugin that will do that?

Thank you.
-Cheryl