I also belong to the thin type, but now I am fat and much stronger than before. According to my own experience of getting fat and strong, I think it is because of exercise and reasonable diet. Let me briefly talk about it, hoping to give you some reference.
First: keep exercising every day. I have a rest after lunch at noon, and then do the horizontal bar and parallel bars (the standard adds up to more than 30 times). After dinner at night, walk for half an hour, and then come back to make dumbbells (100 times, divided into two groups), arms (90 pieces, divided into three groups), 60 push-ups (normal 30 pieces, divided into two groups), small ones.
Second: eat three meals a day on time. Eat three meals a day on time, and sometimes you may not want to eat. Just tell yourself in your heart that it is not good for your health if you don't finish eating, and silently remind yourself that your appetite will gradually increase. Pay attention to supplement protein for three meals and eat more fruits and vegetables; Besides the normal three meals, you can give yourself some biscuits, chocolates, etc. In the middle of three meals, step by step according to personal circumstances.
Third: Hint in your heart. When you can't eat any food, you should remember to tell yourself that you can gain weight only if you eat it (similar to the second point). It is shameful to waste food, so you will become a habit unconsciously.
This is my own summary, and it has already had obvious effects for me. I think thin people will increase their demand and absorption of nutrition after exercise. After a long time, you will form good habits, and you will find that you are not only fat, but also perfect.
Some people are thin, but they can eat, but they are not fat after eating. This should be because they don't absorb it, perhaps because their intestines are not good, but this is on the one hand, mainly because the absorption ability of cells is not good, so they want to exercise.
Just like losing weight, gaining weight is a gradual process. Don't take medicine blindly.
The above is my own experience. Of course, not all of them are suitable for you. I'm also glad to hear other people's answers. I'm glad to hear that anyone wants to share their fitness experience.
Finally, I wish you get fat as soon as possible, fat and strong, perfect man!