Go inside the library and talk to the portrait asking for the headline of the Daily Prophet. Then head to the Great hall and walk up to the front table. Face the crowd to see a podium with candles on it. Cast Depulso to earn Discovery Points and Incendio to make the candles appear all over the place. Now cast Wingardium Leviosa and an owl will come by and drop a newspaper on a table near a Gryffindor student. Examine the paper and go back to library to talk to the portrait again. The portrait will then tell you the password that leads to a shortcut to the fourth floor, which is “No news is good news”.