Sounds like you are starting out on the right track. 3-4 days a week should be plenty as long as you optimize your time in the gym. Heres a few basic guidelines for you:
- More muscle will help to burn more calories, so you need to be lifting fairly heavy to get some good lean mass.
- You need to make sure you hit every major muscle group at least once a week. If you are doing a full body workout each session, make sure you allow at least 24 hours between workout days so your muscles have time to recover. (Cardio is still okay if you want to do that on "off" days).
- It's better to do resistance training before your cardio so you have more energy for the weights, but however you're most comfortable doing it is fine.
- Diet is still going to be crucial to losing fat. Working out will probably help, but all the working out in the world won't compensate for a crappy diet. You need to eat fewer calories than you burn each day and try to be careful about what you eat (which can be hard as a freshman, I know). You'll also find you have more energy and generally feel better.
- Drink 2-3 litres of water a day. Keeps you full, hydrated, and helps the body work efficiently.
Just some basics. If you have any other questions, theres a lot of helpful people here.