Before the event starts, monitor your poster subsessions to check whether delegates have posted questions in the Q&A board. If you can answer those questions by text, you can do it right away, there's no need to wait for the day of your live presentation.
If you have questions about the poster presentation "mechanics", don't miss the "Q&A Virtual Conference" session on Monday, 14 September, 15:10 UTC. The organizers will be available to clarify your doubts and listen to your comments and suggestions.