I am a 22 year old male who is 6 ft 4 in. i weigh 162 lbs, should i gain weight by eating a lot or will i gain as i age. i have never exceeded 170 lb?

Nah.: As long as you have a well rounded diet, then weight isn't a big issue for you. Don't worry, age will catch up and add some weight down the road. I was 6'5" and 175lbs out of high school and I have had no problem adding to that over the last number of years. The key is healthy diet and exercise.

Weight gain: At your current weight and height you have a BMI of 19.7 which is still within normal range. The weight that we gain as we age is usually fat. If you want to weigh more, consider building bulk. Eat healthy foods high in calories. Eat 6 meals /day. Work on strength training to build large muscle groups. Work out w heavier weights w fewer repetitions. Sleep at least 8- 9 hrs/night. Hydrate well