Let say the impossible happens and i found some private key.....how can i test it? I have installed Bitcoin Core5.7.1. How and where to put the private key? Step by step please. I'm new in criptocurency. Thank You.

Hi every one!
I just join in the forum. I have a question: Did someone tried to find the origin of the painting? Who is the author of it?
Or this is made by the creator of the puzzle??? Maybe we have to start from there(or at least me)