"I feel you pain"- I graduated HS @ 6'3" & 125lbs- holy cow! Now I am @ fluctuate between 215 and 220lbs, yes almost 100lbs heavier.
EAT- I eat 6x's per day, 500 to 600 calories per meal=3000 to 3500 calories per day, you must eat every 2.5 to 3 hours. I try to get 30-40 grams of protien w/each meal= 200-240g per day. Eat good foods, lots of fruits and vegies...stuff your body can use. You can pig out on fast foods some, not all the time. Use protien or weight gainer shakes for your meals in between breakfast lunch and dinner. Take a good multi-vitamin.
LIFT- hard mass gaining lifts- squats, deadlifts, bench, bent over rows, straight bar curls...these require lots of different muscle groups, puts stress on your body to release growth hormone. Don't waste time & calories doing set after set of completly isolating lifts like concentration culrs. Keep you sets to 3-4, 6 to 12 reps- HEAVY. Give each muscle group time to rest, at least 72 hours.
DO NOT DO ANY CARDIO!
SLEEP 8 to 10 hours daily, if you can.
Research "Ectomorphs", that is the body type we are & will give you more good tips.
The idea is to tear down, supply w/constant source of nutrition, & rest to rebuild.
Be consitnant, each day at a time.
You will gain 1 to 2 lbs per day week...I promise.
Research "Ectomorph", that is the body type we are, we are cursed! but it can be done