The same way that you would add any other text field.
http://osticket.com/forums/showthread.php?t=13974(http://osticket.com/forums/showthread.php?t=13974)
It did not work.
What I want to do is when printing the ticket down there and a line appears below the name of the client's ticket.
Thus as the client has become aware that signed the ticket requested.