Use the exhibition name as the title of your source, followed by the opening and closing dates of the exhibition, then the museum and city as the location.
Pink: The History of a Punk, Pretty, Powerful Color. 7 Sept.- 5 Jan. 2019, The Museum at Fit, New York.
List the name of the designer/artist as the author followed by the name of the piece/artwork.
Lagerfeld, Karl. Chanel Ensemble. Pink: The History of a Punk, Pretty, Powerful Color. 7 Sept.- 5 Jan. 2019, The Museum at Fit, New York.
Original Artwork in Museum:When citing the original artwork (like a painting you saw in a museum) include the city the museum is located in:
van Gogh, Vincent. Self-Portrait with a Straw Hat (obverse: The Potato Peeler). 1887, The Metropolitan Museum of Art, New York City.