To do so, log in normally with your email address and chosen password. On the top of the page, click on "Add code". Please type in your child's invitation code. Then you will see your child's name and school and will be guided through the rest of the process. After successful connection, you will see your newly added child's name on the start page.
How do I add another child/class to my account?
After you have registered once with the invitation code, you can add any child/class to your existing account.