allegro pcb auto place tutorial
There are dozens of different PCB and Schematic editors.
Cadence Allegro, Orcad, Mentor PADS, Altium Designer, Protel, Pulsonix, Eagle, PCAD, Cadstar, etc, etc...
In addition to the various brands, there are different versions. For example, Allegro 14, 15, 15.2, 16, 16.1, 16.2; Altium DXP2004, Altium Designer version 6, S08, W09, S09; Protel 2.8, 3.1, 98, 99SE; etc, etc...
Within the Cadence versions there are various implementations. For example, Allegro PCB Designer XL, Allegro PCB Performance Option, Allegro PCB Design L, and PCB Designer.
Since you are a beginning student, I think you need to start by running the tutorial that comes with the software you have. The tutorial is intended to answer basic questions regarding the use of the software. Once you have learned the basics regarding how to run the software, you'll be able to get the finer points explained here.