Weight loss for college kid?

I have always been a rail thin kid and could eat anything i want to and not gain weight. After i hit 18 i am 150 pounds (i am 5'7") and i know that is a normal weight, but how to i get these cottage cheese theighs that i never had before to go?? I mostly wanna get rid of this muffin top i have obtained. I need an excersize routine that is good for me, college kid with an office job and i need a diet! I miss my skinny body! Help!