Mk8-usa-dlcs-loadiine-ziperto.rar
Loadiine is considered an older method of playing backups. Most users now prefer WUP Installer GX2 to install games directly to the Wii U menu or USB storage, as it offers better loading speeds and online compatibility.
Loadiine expects a specific folder path on your SD card: SD:/wiiu/games/Mario Kart 8 [AMKE01]/ (The base game) MK8-USA-DLCs-LOADIINE-ZIPERTO.rar
If you are using the Cemu Emulator , you can install this DLC by selecting File > Install game title, update, or DLC and navigating to the meta.xml file within the extracted DLC folder. Loadiine is considered an older method of playing backups