Supplements for adding bulk.
1-Fish Oil (buy in capsule of bottle form, consume before every main meal. Aim for 15g per day)
2-Whey Protein (add carbs to the mix if you are 12% body fat or below, otherwise add glutamine instead). Consume 40g or protein straight after weights and conditioning sessions.
3-Eat a lot of meat (both red and white) and good carbs.
Otherwise there are no secrets to putting on mass, except train hard and eat big, and rest well.