How do you gain muscle if you are a vegan?

Exercise & protein. Many vegan foods, such as nuts and legumes, contain protein. Strength training and protein equals increase in muscle.
Soy protein is... Soy protein is not complete for humans and its ratio of essential proteins means you need almost 4o percent more. It does not contain methionine, an essential amino acid. Vegetarian diets are solely a social statement and need substantial supplementation!?!?