You can log in to your personal customer account here. There you can view details of your booking as well as directly upgrade your insurance package.
Click on "Carefree Packages". There you will find an overview of your current package, the upgrades you can make and information that will help you understand the advantages of the Carefree Packages at a glance:
Select the kind of insurance you want and click on "Book now". As soon as you confirm the option, your insurance package will be updated.