Earlier today, I saw pictures of Real Madrid players travelling to Warsaw earlier ahead of their UEFA Super Cup game tomorrow against Italian club Atalanta that'll be played tomorrow and Kylian Mbappe was one of the players in that squad which I think simply means he'll play his first game as a Real Madrid player tomorrow. The big question now is if Ancelotti will make the big decision of naming the France international in his starting XI. Wether he starts or not, I'm 99% sure he'll feature in that game
One thing that is certain is that Mbappe will indeed make his first debut at Real Madrid through this match. Against Atalanta, who are the champions of the European League, it will provide quite an interesting sensation to watch. Even though Real Madrid may be the favorite in this match, Atalanta will definitely provide strong resistance like when they beat Leverkusen. Everyone is probably more curious about how Mbappe's debut will be in this match than the result of the match. 
But I personally have another curiosity, namely that I am curious about what kind of formation Ancelotti will ultimately use. Will it be the same formation as when Benzema was there? and I think it's most likely like that.