im your height and i used to be about 145 when i was 16-17. skinny as fuck. im now 20 and now about 165-170 and gaining. its reallll tough to gain weight i know. but theres a few things to remember.
now, with our metabolism, eating 6 to 7 times a day doesnt really help us now does it, if our metabolism is already hyperspeed, keeping it that way doesnt allow for weight to stay. so cut that down to 4-5 meals a day.
EAT HEALTHY. try and eat nutritionally dense food. my favorites are tuna, any kind of cooked fish, oatmeal for fiber and carbs, fresh fruits for fiber and natural sugars, rice for carbs and fiber. stay away from alot of red meats. milk and eggs help too.
For exercise, dont go out everyday and do cardio. THE TRICK TO WEIGTH GAIN IS KEEPING A HIGHER CALORIE INTAKE LEVEL THAN CALORIE USAGE LEVEL. if you do alot of cardio, youll stay a beanpole.
For muscle growth, lift 3 times a week tops. and lift weigth that is gonna strain your muscle, so maybe 3-8 reps a set tops. i personally only workout every third day. each workout, doesnt have to be long, but the goal is to feel as if youve worn the muscle out that your trying to build. my typical workout is always less than 30 minutes, and targets ONLY my large muscle groups (chest, shoulders, and back...my arms get worked out in the process of doing multi muscle workouts like presses, flys, deadlifts, etc.) I workout every third day to allow 48-72 hours for my muscles to repair the damage done by working out.
i do NOT keep track of calories or protein. i just try and keep a balanced mix of different healthy foods. i stay well fed and that is sufficient enough.
i could go on about little tidbits of info but this can all be done by you by researching the internet extensively as i have. i personally also have my own system which fits my schedule, my food likings, and the fact that i dont take supplements, so you may or may not want to follow my routine or guidelines.
overall i say that you do alot of internet research about
-your body type (an ectomorph if i had to guess)
-healthy eating habits( diet is 80% of a good body)
-lifting routines to get a general idea of what different exercises do(dont pay too much attention because most routines on the internet are geared towards muscleheads, not people who want to get a natural healthy looking physique.)
oh and btw, i smoke a ton of ganj and it doesnt affect anything musclewise. works great to relax after a workout. even arnold schwarzeneggar smoked weed after workouts hahaha.