How can i gain weight? i am 27 years old, weighing 60kg, height is 1.75m. thanks

Go to your PCP.: You need to go to your pcp who can run some tests, such as thyroid tests, to find out why you're not gaining weight.

More calories : To gain weight you need to consume more calories then needed by your body on a regular day. Using the data that you gave, you need more then 1980 calories a day to gain weight. Look up basal energy expenditure for a calculator.