Hi welcome -i can advice to add one protein supplement like proteinx or kabipro / b-protien 2 scoops two times with 150 ml milk. Or lukewarm water.
Diet- you need high calorie diet. That means you have to add quality meals enriched by protein. Add more rice in meals added by butter or ghee, some times fried rice or polao you can. Vegetables soup or strew 2 times, maximim mix vegetables in meals, 2- pcs sweets. In a day. Add sprouts, pulses. Add puddings cream paneer, yogurts, curd as possible. 2 pca big size banana like in break fast & at 11 am. Sleep min 8-9 hours. No stress, more water, electrolytes, fruits juices, banana shake, more importantly add enough protein by milk (d. T or skim), chana, curd, lassi, butter milk also better. Finally I can advice to add one protein supplement.
Only calories won’t add to your body weight,include the right amount of proteins to your diet. Remember if you want to put on weight and look fit, you need to build muscles not flab. Eat -
Eggs, lean meat, fish, pulses, sprouts, and dairy products that rich sources of proteins. Fish such as tuna and mackerel are rich in oil and are one of the best ways to increase weight.