2 g of protein per 1 kg of its own weight, i.e. If you weigh 70 kg, then 140 g of protein should be consumed per day. Better dosed, the body assimilates only 35 g of protein at a time. The main thing in the diet should be carbohydrates, approximately 50-60%, 30-40% proteins and 10 fats. It is more correct to eat 5-6 times a day than in large portions 3 times.
The main feature is that the amount of energy received exceeds the amount spent. In fact, ideally - to eat every two hours so much that you start to feel sick. Just to failure. When gaining mass, I ate about 6 times a day.
Good luck with your training. (I hope there will be time for them in between meals)