I'm assuming you are a complete newbie to exercise & it's nutritional needs because of your previous post? Don't let that discourage you though because you are at a huge advantage. You'll get some really good gains if you

1. Pick a program, stick to it. Do your program for a least 8 weeks. If your results sucked ass then take a week off to reassess. Why 8 weeks? It's the shortest time from my experience for your body to adapt & see results.

2. Eat meat. Real meat like beef, bison,lamb. Not thin slice chicken breast with the fat trimmed off. That's for yoga chicks & rooftop farming hipsters.

3. You're 20yrs old. That means your balls dropped. Im assuming you're a man. Regardless, you're at a very anabolic stage of your life. Take advantage & put serious effort into what ever program you pick.

Well, since you asked, lose everything but the squat, bench press, and chin-ups. Do two sets of 4-6 reps twice a week.

If you don't know how to squat and don't have a good trainer (rare they are) don't squat. Your form will be off and you'll risk injury.

Also don't listen to the squat zealots who insist you have to squat regardless. Treat them like religious fanatics. Smile, nod, and go on about your workout.

you've got http://www.exrx.net/index.html to learn the different movements and to do home training, you can choose elastic bands with body weight workouts and jumping rope for cardiotraining.

You could also try SimpleFit which is a great program based on pullups, pushups and squats