Open the compressed folder, press Ctrl + A to select everything and drag them to the graphicsPacks folder in your Cemu installation. You don’t have to copy them all if you’re just playing a game, but they’re just text files small enough that it doesn’t matter much.
You can download the most important ones from this tracker on Github. Then come to the graphics packages. The graphics packages in Cemu serve many roles, from essential fixes for specific hardware bugs to making the game look or work better, to full mods for Wii U games.