15 year old boy working out: six pack help, building muscle help. will whey help?

hello i am a 15 year old boy, 5'9 and about 140 lbs. i have been going to the gym every now and then and working out but no results bc i wasnt going routinely. Now i am going to take this seriously. i want to have a nice six pack like really defined before summer. i am pretty slim and when i flex in the mirror i can see the outline of a six pack but only in the mirror. also my arms and chest are frail. i want to get bigger and have decent arms and chest. so i heard whey protein in shakes helps build muscle. i also heard that it makes you gain weight. I obviously dont want to gain weight because that will mess up my chance of a six pack. also what are some good ab workouts. i have a gym membership to planet fitness so if any of you are familiar could you tell me what machines will help me work on my arms and chest. thanks a lot