Bulking 101:
Cardio is a form of aerobic excercise (meaning with oxygen) and is any sort of sustained repetitive movement for long duration (rowing, swimming, biking, running, sex - if you're doing it right, etc). Aerobic excercise is not your friend when you are attempting to gain weight for multiple reasons.
1. The most fundemental part of bulking is to gain weight through increased caloric intake and decreased overal physical activity. If you do cardio you are using up the fuel that you are putting in, there by negating the purpose of bulking in the first place.
2. Even more importantly cardio had been proven to increase the release of the stress hormone Cortisol which does two terrible things to a would be bulker. First in lowers testosterone levels (alot) and testosterone is the hormone that regulate tissue growth and protien synthesis. Secondly Cortisol increases fat storage. Which is why distance runners have a tendancy to be "Skinny Fat" meaning low muscle tone and still flabby.
Weight training is a form of anaerobic exercise (meaning without oxygen) and is used for short duration, high power output movements (sprinting is another example of anaerobic exercise) This type of exercise is proven to increase testosterone levels and muscle synthises. Specifically doing progessively heavier weight, compound (meaning using multiple muscle groups at once, ie: Bench press, dead lift, squats, etc) exercises and High intensity interval training ie sprints.
Fueling the machine is one of the most critical componants to gaining muscle mass, it doesn't matter how much you lift, if you don't put gas in the tank, you won't build anything. You must eat enough macronutrients (carbs, fats, protiens) to fuel and rebuild broken muscle or you will never gain muscle mass.
Rest is one of the most often understated concepts of bulking, your body builds and repairs muscles primarily when you are at rest, which is why sleep is critical, getting the right amount of sleep is also important to ensure you hormones are properly regulated, to little sleep and your cortisol levels rise while your testosterone levels drop.
Those are the basics...