To change your Lufthansa flight, visit the Lufthansa website or use the Lufthansa app to access your booking. Log in with your booking reference and last name, then select the option to modify your flight. You can adjust your travel dates, times, or routes, depending on availability and fare rules. Alternatively, you can contact Lufthansa's customer service for assistance. Note that changes may incur additional fees or fare differences, and policies can vary based on your ticket type and fare conditions.