Need to make reservation (only) for PKP-Intercity...but how?

I was able to enter a "season pass" as a discount code that then allowed me to purchase a seat reservation only. But I didn't find a Eurail pass among the discount codes for that same purchase.

I then found this information on the Intercity site:
https://www.intercity.pl/en/site/for-passengers/offers/special-offers-for-international-transport/oferta-interrail/rezerwacje-miejsc-kompendium-wiedzy.html

How to book?
Seats can be booked up to 60 days in advance of the
planned journey at international PKP Intercity ticket offices*. Online
at interrail.eu from 3 months to 7 days prior to the planned journey.

Perhaps someone else will know definitively if it is or isn't possible to purchase your PKP Intercity seat reservation with Eurail pass. But you might also try using interrail.eu.

Jenifer, I don’t know the answer to your question, but assuming you have a timed ticket for Auschwitz, you may want to investigate the bus. If your train is late (it happens), with only one train, you might be stuck. The bus is easy to use and it’s not expensive and they are quite frequent. You can get the schedule at one of the (official ) tourist offices. Check RS book for details.

You may also want to investigate if a Eurail pass is the way to go. Trains in Poland are not expensive. You can buy point to point tickets and reserve seats on line. We did most of our travel, but we took the bus a few times.

Hope you have a good trip.

Assuming you will be in Kraków at least one day before, you can undoubtedly get your reservation at the railway station. The chance of this train being fully booked, is minimal.
Alternatively you can buy tickets in advance with the accompanying reservation at the PKP site. They are a mere PZL 21,00 (less than USD 5,50) one way, which also illustrates the point made that Polish trains are incredibly cheap and that a rail pass is probably not the most economical way to travel (and certainly not using one of your rail pass days for this day trip).

Thank you everyone for the help.

I always search other posts before I ask a post to see if I can find the answer first. So in case anyone is looking to do the same:
No I can't book reservations with Eurail.
No we don't want to take the bus. The book says it fills fast and we're just more comfortable with trains.
Yes it doesn't seem that this daily train fills and yet I keep seeing that you must make a reservation. Odd.
Yes, I'm using a Eurail pass because Poland isn't the only place we're visiting on this trip. Even if it was overall slightly cheaper to buy all those individual tickets, the convenience of just having a pass that I can fill in and use as I need is worth it for me.

In the end I spent way too much time on this! facepalm I continually overlooked a regional train that runs 10:31 to 12:10 and requires no reservations. It barely takes minutes longer. We love using local trains and this is an excellent solution. We might even rent bikes to take but that's a different story.

Thanks again!

You must make your free reservation at a train station in Poland and the same applies for other fast trains in Poland. Reservations are not required because the train is likely to fill up, they're required on other principles, as in some other countries.

See also:
https://www.ricksteves.com/travel-tips/transportation/trains/reservations and
https://www.ricksteves.com/travel-tips/transportation/trains/poland-rail-passes.

OK so now I've circled back to the original problem.

I need to make a reservation for the night train to Budapest and yet I can't find how to do it online. It's an IC-Intercity.

The links in Rick's site just sent me to Rail Europe to buy a pass and there is not a way to make a reservation or even buy a ticket. Although there is much caution about reserving ahead because of limited seats...exactly why I'm trying to do this before I arrive in Poland!

I tracked down the actual rail line again and the intercity.pl site has a trip planner feature, but I can't make a reservation. It literally says "You can buy a ticket for this connection at the counter."

I found a way!

As I said, I read other people's forum posts a lot in an effort to help myself before asking. So in the spirit of helping someone else:
booking.polrail.com
International trains (big picture on the right is clickable)
Drop-down menus to select cities
Enter number and gender of passengers
There is even a checkbox "Click here if you have Interrail or Eurail Pass and you need only seat / sleeper reservation"
I can even reserve the type of couchette/sleeper I'd like.

The only thing that this lacks is the option to sleep together as husband and wife in one double car as I've done using other bookings. But HEY travel is all about adventure right?! Let someone else listen to my husband snore instead! Maybe I'll make a friend!

shop.acprail.com works the same too!

To answer my original question if I want to reserve the train from Krakow to Oswicim, then I need to reserve the IC from Krakow to Prague and just get off in Oswicim. I would do it using booking.polrail.com. 92 PLN / 23.5 USD!