This is so key to your success in putting weight on.  You can lift for 5 hours a day 7 days a week 365 days out of the year, but if you do not eat the correct food you will not gain the muscle mass you desire.  Food helps you add weight because it repairs your body from being broken down from the strength workout.  
Now!  you need to put the right things into your mouth.  Eating everything in site is not going to get the job done of adding strength/size.  You need to prepare your meals and have them ready for the day.  Looking at adding size you want to eat between 5-6 meals.  These meals need to be spaced out throughout the day.  For example:  Eat breakfast at 6am, Snack 9am, Lunch btw 11-12pm, Snack 3pm, Dinner 6pm and Snack before bed.  You need to feed the machine that is yourself.  
Looking for good ideas of what to eat? Direct message me or one of the EXSP trainers and we will help get you the information you need.

Greatness Never Rests