On iOS: On the search screen, tap the gear icon below the To and From search fields. Then select your desired currency from the list that appears.
On Android: Tap on profile tab in the top right corner. Then tap on the Settings gear in the bottom right. Finally, tap on Currency and select desired currency.
Please note that due to U.S. travel agency regulations, Hopper must charge bookings in USD, which will be noted on the payment screen and on your receipt.