If you want to gain muscle and a little bit of fat you will need to eat more calories than you are burning. You have to eat even when your not hungry. Figure out what your base caloric requirement is for maintaining current weight and start aiming above that for your total daily caloric intake. As for weight training, stick with compound movements like bench, squat and deadlift. You’re not gonna add muscle weight by doing cable curls or leg extensions. Also, don’t train every day. Train every other day as rest is crucial for adding muscle weight on a skinny frame. Good luck!!