You can make the following types of changes through the 'Manage a Booking' section on emirates.com:
Flight itinerary:
General booking changes:
If you need to make other changes, please contact your local Emirates office. If you have booked through a travel agent and have not yet started your journey, we recommend you contact your agent to make any changes.
There may be a fee associated with making changes to your booking depending on the fare conditions of your ticket.