Hi I am going to City College as a freshmen & I'm confused?

Hi I'm sorry I do not know jack thing about college & I decide to go to City College & take general cles & hopefully I could transfer to University. I did decided to join the U.S.military but, I think I'm going to waste 4 yrs & I'm 25 yrs old. Yes I finish 4 yrs in high school & I do not know what to do with my life & I do not want to be a server for career. I always wanted to be a U.S.military officer or firemen but, first thing first, I need to go to college & what is your suggestions? Thank you for your kindness.