ok Eugenia i see the keyframes, i clicked on them but i'm doing something wrong. can you be a little more specific?

You'll have to experiment with keyframes.

At the beginning of the text timeline there's a keyframe (diamond)there already. Move the timeline cursor down to the three second mark, and then change something concerning the text, say, the color. A new keyframe will be added automatically. Now play the text on the main timeline. It will do that change you made in those three seconds.

Do a search on YouTube for Vegas Keyframes, because sometimes it's just easier to see how it's done.