Okay, I think I've got this licked. When running the game in BlueMSX, first select File -> Cartridge Slot 1 -> Insert from the menu. Choose the game (typically "whackem_msx.rom"), then select "SCC" or "Konami SCC" as the ROM type. I'd recommend using C-BIOS as the BIOS, since it comes with the emulator. That can be changed in Options -> Emulation. Make sure you have the BIOS where BlueMSX can find it, or nothing will happen.