1. Reasonable nutrition collocation: eat more foods rich in fat and protein, such as fish, eggs, dairy products and beans. These foods can help you gain weight and build up your physique. At the same time, we should also pay attention to the collocation of food to ensure adequate intake of nutrients.

2. Increase the intake of carbohydrates: carbohydrates are an important part of weight gain, and you can eat more foods rich in carbohydrates, such as rice, bread, potatoes and sweet potatoes.

3. Proper exercise: Although exercise can help you consume energy, it can also enhance your physical fitness. Proper exercise can promote muscle growth, enhance the body's metabolic function and help to gain weight.

4. Avoid overeating: Although you need more food to gain weight, don't eat too much at once to avoid overeating. It is necessary to gradually increase the intake of food and let the body gradually adapt.

5. Diet rule: ensure three meals a day, don't skip meals, and don't be too hungry.

Please note that weight gain also needs to be moderate. If you are healthy and have no disease, it is recommended to do it under the advice of a professional doctor or dietitian. If you can't gain weight due to physical reasons, please follow the doctor's treatment plan.