I was involved in a national power gymnastics program at Penn State. Was not the most talented but perservered. I got a chance to work out with some amazing atheletes. Also saw genetics at play with muscle size and strength. Some guys had big muscles but were not a strong as small muscled guys.

I never could build big muscles - at one time could bench 210 lbs and weighed 134lbs.

I know the basics are that you must lift heavy weight with low reps to bulk up muscles aside from the food requirements. Just keep in mind not everyone can develop big muscles at least in my experience.