One of the best things pretty much every post secondary school offers is a gym on campus or nearby. This is a great resource close by that you can use whenever you want, and if you want to keep the freshmen 15 off you should take advantage of it.
Step 1: Find a basic routine
Make sure that you find a routine and stick to it, consistency is key to success. You can find routines on any major site like www.bodybuilding.com.
Step 2: Use supplements
You can dramatically improve your results by using supplements because they can improve your focus and energy levels. In particular, pre workout energy drinks can really help.
If you don’t want a full pre workout supplement you can try creatine as well to help solely with your energy levels at the gym. You can learn more about the science behind creatine at http://bestcreatines.net, but sufficed to say it will help you train heavy for longer.
Finally, keep it simple and have fun!