How to edit or deactivate an extra :
Click 'Manage extras' button in the menu. So you can see your activated extras. You can edit or deactivate them.
For editing, click 'Edit extra'1 button.
For deactivating the extra click 'x'2 button
General view of Your extras page:
Click 'Manage extras' button in the menu. So you can add a new extra by clicking 'Add extra'3 button! After selecting the extra4, click on 'Add extra'5 button! OK!
General view of Add extra page:
After adding an extra, do NOT forget editing the extra's options!!