Together with the person you are assisting, meet the moderator before the event
Explain how the person you are assisting communicates and how they want to participate at the meeting
Find out how the moderator wants to conduct the meeting and if they want (a) participants to stop talking and wait for the person to communicate their message during the meeting; (b) schedule times throughout the meeting when everyone can contribute opinions and questions or (c) wait until the end of the meeting for Q and As.