When you get control just keep killing all the skeletons until voldemort casts
aveda kadavra on you. Then just move that around killing all the skeletons until
voldemort will cast a big statue at you. Just run away from it and kill all the
skeletons now try to destroy the statue whenever its on the ground with the
spell, after its destroyed youll see harry dragging cedrics body. Voldemort
will go to attack harry but he uses accio to get the cup and return back to
hogwarts.

Congratulations on completing Harry Potter and the Goblet of Fire, now after
the credits you can return to each level and collect and of the shields or
anything you may not have gotten, you can do all the subquests, and obtain
all the cards you have not gotten yet.