you see a red chat box in the lower right-hand corner of your screen. do not expect much, my experience so far with them is useless, tried at least three times, and every time, it's not an expert, just someone asking you to read the manual or have no clue whatsoever on any topic ;-(
Thanks for the screenshot @Walid . @wwwyzzerd You also need to make sure you have the Standard subscription. Note that the chat is used to assist you through your courseware, and not to assist with technical issues on the platform. Availability for exact content experts may vary, depending on when you reach out, so that may affect your experience and support.