The way to accept in Family, living in a different country

I have iPhone 6s Plus. My daughter sent me an initation in Family from Germany. I tried to accept this invitaiton, and confirm botton too. After that, botton Continue and then it says:

I must change my account in Germany in ajustment of iTunes Store and App Store, so I go to Ajustment

But then I cannot find any place to change there.

Do I have to change my ID Apple?

Please help me!