Before you press OK, make sure that your Elements are in the order you want them to appear. If you want your intro to come first and it is listed second, simply select it and press the up/down arrows indicated in the the picture in order to modify the element's position in the rollover.
Finished!
Press OK, and Dreamweaver does the work for you. Your page should look something like the one below. Play with your naviagation bar to make sure it works. Congradulations, you've just made a navigation bar rollover!
