There is an Iowa National Guard app available in the Google or Apple store. This app will let you search for careers, find a recruiter, etc.
ROTC is an elective curriculum that you take along with regular college classes. You have a regular college experience, but the ROTC training prepares you to assume a leadership (officer) role in the military when you graduate. By enrolling in an ROTC program, you can get help paying for college. Different branches of the military have ROTC programs at various colleges; this option is not available at all colleges.