You are going to go through ROTC, correct?
You need to do well in that. Various factors (GPA, PT scores, your commander's recommendation, etc) will determine your ranking. If you rank well, you will have a good chance at getting a pilot training slot. Once you get a pilot training slot, you can go to UPT (pilot training) after graduation.
UPT is about a year long. It starts with ground school, then moves into flying. Expect a lot of studying and 12 hour work-days. Your duties, other than flying, will depend on what your squadron needs. It could be something as simple as running the squadron snack shop, or something more complicated.
The Air Force will help pay for your schooling, but your duties may determine what kind of schedule you can take. Also, you may incur extra time commitment since they will pay for your schooling.