After Claudius so abruptly leaves the play, Hamlet feel confident, because by Claudius leaving the play, he knew that Claudius is guilty of murdering his father, Hamlet was able to prove his point and confirm the suspicions he has about Claudius.
You press the bar that tells/ask you to aswer it and you type the answer in and in the right top corner a green icon says "Add your Answer" and thats it.