Callback lesson please please

Hi There;
RT-3.6.4

Can someone give me few lines on how to use callbacks to customise RT,
I’ve installed shredder for the only purpose of learning how it used
callbacks, but it just added to my confusion , I want to add the
CreateChildTicket callback as described in the Wiki but I am failing to
see any buttons in my display …
Can anyone help please??

Regards;
Roy