Stupid me. Now I know what you want. The bad news is you can't do it in the standard version of Studio. You need an editor that can work with at least two video tracks. You can upgrade to Studio Plus, or find another multitrack editor. Once you find that program, create a still image containing the text you want, 2-colors only (one for the background and one for the text), make the text color transparent and save everything as GIF or PNG (to mantain transparency). Or you can make that color transparent directly in the video editor. So place your video on the first video track and the still on the secondary track, adjusting its duration as necessary. And that's it.