Just klick on Premium (next to the Ranking). I have no clue how the option is called in english and i do not have premium points so i do not have it, but it should be something like "use premium points". There u have to choose the word wehere u want to use your premium points. Of course threre is only one. Thereafter i think to have to logout and than it should work. But do not be confused it lookes a littlebit different, but u get used to it quite easy.