In this context, Stephen (the interviewer) is not asking a question. He's telling the actress to explain to the audience about a previous time where she played twins.
Prior to making this statement, Stephen mentions that Julianne's current acting role, is that of a pair of twins. He then mentions that this is not her first time doing so and when Julianne agrees with him, he then makes the statement "Could you tell people about your experience playing twins before." which prompts her to speak about her previous role on the show As The World Turns, where she also played a pair of twins.
In this context, the sentence is perfectly fine and understandable.