Weight Gain For Fitness

Hi. From the beginning, I tell you that I want an opinion only from the well-versed on the topic, not from the sulyu and pulyu who have no idea what diets are, and they only come to express their incorrect opinion :). I work office work, eight hours a day I sit in front of a computer, with almost no getting up. I felt very stiff, and decided to listen to my colleagues who advised me to enroll in the gym. The problem is, I'm 195 tall, and I only weigh 68 kilos (whatever you want, so understand it), that is, I'm a living stick. I've been reading articles on the subject for days, and I've seen all sorts of recommended - from fruits and vegetables, to weight-gain jam. I try to eat profusely, but I'm not the kind of person who can eat every two hours. I usually love and emphasize meat/fish and salads, i like sweetness a little bit. Please once again if you do not know do not comment, or at least be the kind of - "I am not familiar, but I think this and this would have an effect". Have a happy day.