find out your bmi and then work out how many kcalories you need a day.
Use this site
Add 500 kcals when trying to add mass, subtract when removing fat.g
Get your total figure then work out what protein:carb:fat ratio you want to use, generally 40:40:20 but definitely no lower fats than that.
Carbs and Proteins are 4kcals for each gram, fat is 9kcals a gram, so if you were eating 2500 kcals using 40:40:20 you'd have
Protein = 2500x40% = 1000kcals = 250g
Carbs = as above
Fat = 2500x20% = 500kcals = 56g
You dont have to be 101% accurate so round your figures to the closest, easiest numbers.
Whey protein is no magical way of bulking up - it is no different to regular food in terms of what it will do (ie if you eat more than you need you will gain fat, eat less and you'll lose body weight.).
It is, however, good post workout and a convenient way of getting protein into a diet where it normally wouldnt be, especially as it mixes well in oatmeal, muffins etc etc. It can also work out a cheap way of getting your proteins in, as (ie) 250g of chicken, fish, meat, eggs etc a day is costly. BUT whey is not a replacement for food, it is a supplement. I use it in oatmeal, Post WO, smoohies and when im not able to get near decent food.