If you want to get big, gains are made in the kitchen. Lift heavy like he said 6-12 reps, or even heavier like 4-8 or 4-6 and eat like a fucking horse. Depending on your body's metabolic rate and or body composition, you either need to eat strict and clean, clean, or semi-clean. I my self eat anything and everything. I put on a bit of a belly after 20 new lbs (granted it's not pure lean mass), but that's mainly a bunch of bloating from all the food and drink. If I take a rest week from all the eating, the bloat goes away.
You don't need to change anything up unless you stop gaining; just eat and train. If you are eating the same amount every day doing the same routine you have been doing and you stop gaining, then maybe you need to switch it up. But until that happens, why stop while it works? Everyone is different. You can also limit gains by switching up your routine too often. Try heavy sets for 6-8 weeks of 4-8 reps or 6-8 reps with a 2-3 min rest time and eat like a horse, see what you gain. Or try something with a higher intensity with 8-10 or 10-12 reps and like 45-1:30 sec rest time eat like a horse and see what you gain, and go from there. The hardest part (at least for me) is the eating. The training is the enjoyable part.
All I can say is if you are lifting and not putting on weight, it's not because your training is wrong or bad it's because you are not eating enough. I let the myth about ectomorphs haunt me for years, truth is I was never dedicating my self enough to achieve the goal I wanted. The best thing to do is set mini-goals, while having ONE ULTIMATE goal. The mini-goals are there to keep you motivated to achieve that one ultimate goal you have in mind. If you want to be 10 lbs heavier, set a goal and a reasonable time-frame, not something unrealistic like 2 days to be 10 lbs heavier, but maybe 2 weeks or 1 month.