You can modify your listing by accessing My Account, Listings and then select the listing you wish to modify. Then, click on Edit listing
Those are the options available:
IMPORTANT TO KNOW!
Once a buyer buys tickets from that listing you will longer be able to modify the listing. If any or all of tickets remain unsold, the modifications will take effect upon these tickets. As such, changes will not be reflected in any of the tickets that have already been sold.