There's been a few threads on this sort of thing, so if you can spend the time and search them out -- impossible to include so many great hints and tips in one post.

Adding a very slight bit to what Marty wrote...

Very generally speaking, if you take one video stream or file, reduce it's frame size and place it where you want in a full sized frame, fill the rest of the frame with black, and place this track above that with the newscaster in the timeline, you're there -- just play with the composite &/or child track controls.

Alas, there are a lot of ways to manipulate the background video, from creating what you want in another app, to using various colors other then black (just think you'll be surprised how easy Vegas handles that) and so on. You can create a mask track that feathers the edges around your background.

If I misunderstood & you're going for a virtual studio sort of thing (not just imitating the monitors behind the guy doing the news), as Marty said you just about have to Chroma Key, or else move to something like commotion or better.

mike