When you say "i want to widen my torso", I imagine you are trying to achieve the "V" shape? To get wide, there are two things you need to work on: The shoulders and the lats.
Shoulders:
-barbell/dumbell shoulder presses.
-barbell behind the neck shoulder presses, but I don't recommend doing this if you aren't experienced. But if you want, try lowering the bar to only the forehead level, and stop if you feel something hurting.
-lateral raises, which build up the medial deltoids, and gives width
Lats:
-widegrip pullups, or pulldowns on a machine if you can't do pullups. The key here is to lower yourself slowly, instead of just letting your body drop. This adds width to your lats
-Rows (barbell, or on a machine). This adds thickness to your lats.
Although doing bench/squats/deadlifts don't directly make you wider, these heavy compound exercises recruit a large amount of muscles, which increases your body's natural testosterone output, and helps you develop muscle in other areas of your body.