Welcome, YellowSubGirly!
Oh, I remember how hard it was to eat healthily in college -- temptation is everywhere!
As far as how much to run, in my experience, 1 mile running/walking is not enough to yield any results. I think you would need at least 30 minutes of exercise, intense enough to get your heart rate up, to see results. It could be running, walking (especially if you have big hills there in Colorado), or hitting the rec center and using the machines. To build gradually, you might consider the
Couch-to-5K program. If you check out the exercise forum, you'll see lots of people there who are working through one of the many versions of C25K.
The other thing is that all the exercise in the world won't get rid of extra fat/flab unless you are eating fewer calories than you burn. Because you are young and thin, you can very likely do this just by reducing your portions or eliminating/limiting some high calorie foods from your day-to-day diet. Many people on 3FC (myself included) count calories to keep close tabs on calories consumed. Running (or any exercise, but in my experience, especially running) can make you hungrier -- if this causes you to eat more, you won't lose any weight. This is why some people consider running not so great for weight loss.
I should add that I find running excellent for toning the legs and butt! I run about 5 miles, 4x/week, plus one day of cardio kickboxing, but I've been running (on and off) for 18 years.