You need to join your EDMODO class to do portfolio tasks/ assignments, to participate in lesson activities, to access extra materials shared by your instructors, and to communicate with your instructors and classmates.
You can find your class code in the link to join your class.
Please read the EDMODO Student Guide in the link if you do not have an Edmodo account, and follow the steps to create an account and join your class.
EDMODO Student Guide also helps you to find out how to submit tasks/assignments, how to take part in post discussions etc. Remember to read each part in the guide very carefully not to have any problems during the lessons.