Squats
Squat is the best exercise for lower body muscles.
This helps you big legs and quads. For beginners you should do squad without
weights.
Deadlifts
It helps for gaining alot of muscles in your skinny frame. It include upper and lower back , arms , abs and upper legs. It is a great exercise for your back. It is important to have proper and keep your back arched, otherwise your back can injure.
Bench Press
Bench press makes your upper body muscles. This is the perfect exercise for your chest. Many people try to lift heavy weights for gain bigger chest but unfortunate they fail due to bad technique. Lift comfortable amount of weight and focus on technique. So you can lift more weights and also get better results.
Chin Ups
It helps to build forearms , tricepts , upper lats and back. This is good for building back and arm muscles together. A wide chin grip build your lats and back more.
Military Press
This exercise is good for upper body specially for upper arms and shoulders. If you want a powerful and wide shoulder look you should do this exercise. Make sure that your back and buttocks kept press against the back of the seat.