I'm not sure what your concerns are. According to your pic, you look pretty good for 18 yrs old.
However, if you're looking to increase size (which I'm currently doing - and I have a VERY hard time gaining mass)... here's what I'm doing:
First, CUTEJOCKMASC was close, but the average male body can only digest, properly, about 100-150 grams of protein a day - the rest, stored as fat or released.
Correct on weights though - you have to go heavy to force the muscles to grow - you also have to change your routine - average of every 3-4wks - to 'shock' your muscles and prompt new growth.
And food - man, you have to eat and eat clean. By clean, I mean, no fried or fatty foods. And stay with foods high in protein, complex carbs and good fats. I'm currently taking in around 4000cals a day with a balance of 50/40/30 (protein/carbs/fats). Eat at least 5x a day - snack in between meals (fruits, etc.) And get about 20grams of protein at each meal.
Supplements - at least a daily vitamin, maybe go with Creatine. You'll see an increase with Creatine (but it's mainly water weight.) I wouldn't try anything else at your age.
If, after all that, you're still having problems. Seeks medical advice - you may have a medical issue that's causing you not to bulk - hyperthyroid for example. Could be anything. Good luck bud and keep pumpin'.