You start with creating a padstack of any shape that you like. Next, you use the newly created padstack when you place a pin onto your footprint.
That's all.
Bear in mind that might seems easier and quicker to ask "how to" but you'll need to read the manuals anyway if you are to use it preperly.
No offence but you must read first the OrCAD User Guide.
And also you can take the footprint from the footprint lib file and change them for your work.
Open "Layout.exe" from your OrCAD installed dir.