first you need to find a pspice model for your part. Sometimes manufacturers provide it, sometimes you can find it on the internet, and sometimes you would have to make it yourself.
As for the how to get it into the simulation, I cant really help you with such and old version as i have never seen it. My vesion of pspice in the simulation profile has a part where you set the libraries used, and mine points to a file "nom.lib" in "C:\Cadence\SPB_16.6\tools\PSpice\Library", which is a text file that lists all the subsequent pspice libraries containing all the provided parts. So when you get your model and find a similar file in your version, you can add your model to it in the same way the other parts are done.
There likely are other ways described in your user manual, like putting the model straight into your simulation data files, but this how i did it last time i had to edit these when i wanted to include some new digital logic gates.