Go to Schedule > Sessions
To moderate and view the questions, click on the session name, on the right side of this view you will see a green button labeled Moderate Q&A. Click on this. Here you can view the questions in real time.
When someone asks a question, it will appear in the Questions waiting for Moderation section. This is where you can choose to accept or reject the question. Use this to collate questions during the presentation, and you can also save them to be answered after the presentation. You can also select whether the question has already been answered or not.