Hi,
I can support the answers of my fellow consultant colleagues. Buy some (don't get too many in order not to stress yourself) case practice books and get a understanding for the structured approach/ frameworks used. Afterwards practice solving the case in front of others in order to get comfortable with a interview situation, e.g. via PrepLounge. Eventhough it might feel uncomfortable at first through yourself into these situation to gain confidence and get feedback on how you can improve further. Sometimes it is also helpful to have a third person just to observe and share detailed feedback on presentation style.
Best wishes, Bianca