How did you go about becoming a civil engineer and why the army?

I???m Ava and I???m a sophomore in high school. I???ve been wanting to go into the US military ever since I was little and over the past couple of years have had a growing interest in civil engineering. Why did you choose the army and how did you do it? I???m not sure whether to go to college and then go into the army or go army and then college. What would you suggest?