on an actual Wii U console to dump their own keys from physical discs or digital installs to an SD card. The Community Path

After that, CEMU will automatically use the matching key when you load a game.

It emulates the hardware. To play an encrypted game file (usually in .WUX , .WUD , or .RPX format), Cemu requires the specific 16-byte Title Key to unlock that game file so it can be read by the emulator.