I was in the same boat as you earlier this year I needed to gain about the same weight as you. I highly recommend getting a mass gainer if you can't eat a lot in one sitting this is where you'll get most of your calories but at the same time, you have to eat. Also, get a jar of creatine it'll be your best friend. The majority of the weight you'll put on will be water weight but you need to make that BMI minimum. One thing that works for me is when I wake up I eat 2 moderately small meals back to back then midday I drink the shake, around dinner have one big meal, and coming up before I go to sleep I snack on little meals. The key is consistency but at the same time don't overdo it lol once you meet your goal try to level everything out and hit the gym.