i want to add/delete some drop down box. And how to fix when creating ticket for client side it will not automatically assigned to the staff member it is possible? Thanks in advance
i want to know where is the source code/file name of the code of this form
This is not a file.
Go into Admin panel -> Manage -> Forms and manage form here as you want.
If you want to add a drop down box, you would want to go to: Admin panel -> Manage ->Lists and create your list.
Then follow the instructions PavelH gave you and add the list to the form.