How to find parts in OrCAD / Allegro
During this process of selecting a part or a library, for PCB and not simulation always add the discrete library.  This has the most common parts.  After OrCad project has been completed, when you open the place a part menu or "p" on the keyboard, you can type a part number or a part type like zener, it will search all libraries and tell you which one it is (library) add the library, select the part and place it.  If you create custom schematic images or modify one in the library, add them to a new library, updates can over write standard libraries and your custom will be lost.  You will have to go to a schematic that used the part and recover it from there.