this depends on what version of vegas you have. if you have sony vegas movie studios, you can only have up to 4 tracks. if you have sony vegas pro, you can have as many tracks as you want. what you would do is just put one track on top of another. if in the generated media, the text looks like a black and white checkerboard, than that means that other than the text, the background is transparent and you can put it directly on top of another piece of text. otherwise, it should have a solid color background in which case you should go to special FX, and choose the chroma key tab. then you can use whichever one you want (it doesn't really matter which one you use), then you use the eyedropper tool, and click on any spot on your computer monitor that contains the color that you want to apply the effect for. whichever track is on top, that is the picture that will be on top.