Hi. You did not enter the play that this question refers to. This makes it impossible for that question to be answered. However, I will try to help you in the best possible way.
As shown in the question, dramatic irony occurs when the reader of a text knows information, which the characters do not know. This information was revealed to the reader by the narrator or by one of the characters, but it was not disclosed to all the characters in the work.
An example of this can be seen in "Romeo and Juliet" where readers have access to Juliet's plan with Friar Lawrence to fake her death. Although the reader knows that Juliet is sleeping, her family and Romeo do not know that.