How often should I have protein powder for weight gain?

As a general recommendation, we suggest drinking 1 serving within a day. A large part of it will depend on the rest of your diet, and how much protein you are consuming through food. The idea is to use the protein powder to help meet your protein needs for the day, along with the rest of your diet. As a general rule of thumb though, if you are consuming quality protein foods throughout your day, 1 serving a day should be sufficient for you.

Some people who have a more difficult time including protein into their diet (such as those following vegan/vegetarian diets) may benefit from an extra serving. If you do this, try spacing the servings out throughout the day. 

If you have a hard time gaining weight, remember that protein isn't the only important thing. Calories are just as important. If you're trying to significantly increase your calorie intake as well, try adding your protein powder to a smoothie. Including things like milk/soy milk, fruit, peanut butter, oats, etc. will greatly increase the number of calories and other nutrients in there (including some extra protein!). This should benefit you more if you are struggling to gain any weight than simply consuming an extra scoop of protein powder.