Hi Maria,
Welcome to alli and good luck with college!
The combination of starting college and trying to lose weight can be very challenging, but you can and will be successful at both! Having the right frame of mind and confidence will make all the difference in the world.
As you said, your work load at school is going to be very demanding and will keep you extremely busy, but there is still enough time to exercise. You must make it a priority just like your school work. Your health is the most important thing in your life!
Since you are just embarking on your diet and fitness program, you should start out with realistic goals concerning the amount of time you spend exercising. You should try to engage in 2-3 cardio sessions and 1-2 strength training sessions per week. That does not mean that you need to be in the gym 5 days a week in the beginning. Try to get there at least 3 times per week and perform both your cardio and strength training work in one session. As your exercise program evolves, you should ultimately try to get in 4-5 cardio sessions per week and 2-3 strength training sessions per week.
Your cardio sessions should be about 20-30 minutes in duration and the same goes for your strength training sessions. As you make progress you should lengthen both as you feel necessary.
The alli site has many great and simple strength training exercises that it recommends that you can start with (there are video demonstrations on the site). On the home page there is a link "watch our health and fitness videos" that you should check out. It will help you get started.
If you have any other questions regarding your fitness program, please let me know.
Good luck with school and you fitness program!
Good Luck,
Paul