Gravity text?

It sounds like you need to learn about basic keyframe animation first. You can do this with two keyframes; the first is your starting point and the second is your ending point (off screen). You then set your keyframes to ease and pull your easing handle of the second keyframe so the movement accelerates more quickly. Adjusting keyframe easing in Premiere is not a great experience, which is why I recommended After Effects if you're going to be doing this a lot, but that has its own level of complexity.