How can we create new padstack & modify existing padstack in Allegro PCB editor ?

Hi.

  I had read the Mitzner Book(OrCAD PCB Editor) and read some of the pdf books on online.Totally me got confused and then can any one help me please????

Still want i want is to create an new pad stack and modify the existing pad stack. Then how can i save it. Please send me the details in pdf format.Reading in pdf is been better for me.

Note: Send the details in PDF format.