When you sign up, it is advisable to complete the Storm missions, to become familiar with the site, to receive credits for the free plan and to receive experience badges. Credits are needed when you have a free plan to take advantage of the various services. For more details go to the plans doc: Plans doc
Complete a Mission
The quest page will be the first page you see on every login, until you complete all the quests. To complete a mission, click the "unlock mission" link to receive the credits and the badge of the relevant mission.