Apply a Mask Shape (Rectangular) to a Color Matte. Set horizontal scale to 100% (if you want a "ticker tape" banner which runs the entire horizontal length) and the vertical scale to however tall your text is. Use Mask Feather if you want a "blurred" edge. Now put it above your shot. You can also use a horizontal Wipe or a Push Slide to fly it in.
I think LiveType has some presets you can use there, as well. I prefer to do it by hand. Call it habit -- don't like to use two programs where one would do the job.