I would like to add some muscle quickly. What do you suggest?

... scle quickly. It rarely happens fast. Give it time and you can probably add 10 pounds of muscle in a year by weight training near your maximum level and eating more high-quality calories (lean proteins, vegetables, whole grains and fruit).

http://www.philly.com/philly/health/sportsmedicine/20130731_ASK_KIMBERLY.html