You need to take a constant intake of protein throughout the day, every 2-3 hours is recommended. I mix whey protein with oats, to make it more of a filling meal, but don't make the mistake of thinking its the be all, end all. Its just a way of getting a quick intake of protein into the body efficiently, no better than eating meat, fish, or beans. To build muscle you can't just have a protein shake at the end of your workout, and think thats it, you need more. Some people make the mistake of thinking these protein shakes, are like Popeye and spinach, I blame the advertisers.