You can join your teacher's EEi class through the My Account section. There is a menu option called Join EEi Class. Choose that and simply enter the School Code for your account. If you don't know the School Code, your teacher can provide it for you.
Let your teacher know you did this as they will need to delete the student profile they created in your account for you. You will come in as a new student and having duplicates can be confusing and cause issues.