I played D3 tennis years ago. You'll do fine. It's a continuation of high school tennis, nothing too magnified beyond this (was my experience).
I originally wasn't going to play when I got on campus. But then, in talking to this intelligent senior girl, who was a runner, about it, she pointed out that for the past four years I'd been outside in the spring playing tennis. . . and would likely want to, once spring rolled around again.
This was true. So I played. Any "coaching" I can give you would be nonsense based on the jot of video you've left here. My guess is that you would find yourself much more dynamic on court, and feel more energy overall, if you could shake off about five pounds. I suppose that's a useful bit of advice I can share, along with the firm advice to pay attention to your grades when you're in college. They matter.
To Praise, To Bless, To Preach--the Dominican Order