Need help with mass gainers.

To begin with, I'm really skinny, been skinny all my life, 173 cm (5'8 feet) and 53kg , in addition to that, I'm a picky eater and always been one.On top of that I also have a low appetite. Straight to the point, I've tried cheap proteins and they somehow worked but I don't like milk that much, today I stumbled upon mass gainer, which didn't know existed till now. I'm quite a beginner and I don't know much about gaining weight so please have it in your heart to excuse my ignorance. My goal is pretty much a modest one I'd say, I want to go from 53 kg to 60kg in about three months. In order to achieve my goal I'm planning on using mass gainers, I've tried to reach 2400 kcal daily but it's difficult for me without junk food such as Burger King or pizzas, but I can reach 1200 kcal pretty easily, 1500 even. The mass gainer I'm planning to get is "​Optimum Nutrition Serious Mass", and I wanted to ask how can I consume it? Would it be stupid to simply mix it up with water? I heard one scoop is around 600 kcal, so a full serving should be 1200 kcal. I know I have to workout or else everything will pretty much go to my belly but all I want is to get "thicker" especially in my arms so I guess I'll have to do a bit of workout ,I'm not planning on going to the gym however I have dumbells and I can use them to my favor. Another question I'd like to ask, which probably should have been the first one, are mass gainers safe for a skinny guy like me? If you have any tips, please let me know!