Where is, what is, and the rules are?
Hi! You need to copy the card sets from the DLC into c:\Users\USER_NAME\AppData\LocalLow\WittyMinx\NSFWSolitaire\CustomCardSets\
When you install the game and the DLC from Steam, they are automatically located in where the Steam installs them. But with a normal download (like from itch.io) you have to handle the DLC content like card sets you'd make yourself in the editor. Those get created in the app's data directory, in CustomCardSets subfolder