Missions are a feature that will allow you to win prizes through the different game modes. They are made of four tasks that you'll have to complete in order to win the prizes. You'll be able to access them in the 'Missions' box in the home screen.
Once you access, you'll learn what you have to do to complete them. As soon as you finish the first task, the next one will become available and so on until you finish the mission. You'll have 96 hours from Monday to Friday to complete the four tasks and 72 hours from Friday to Monday to complete four different tasks.
Once you complete them, you'll have to access the 'Missions' box to claim your prizes.