Where did you (e.g., a specific forum, wallpaper site, or social media post)?
Ensure you have parts 1-8 to ensure the archive is complete and not corrupted.
Place all parts in one folder, right-click on the first part (part01) in your archive utility, and select "Extract Here."
Because part08 is part of a multi-part RAR set, it cannot be used in isolation. To access the final content, you must download all corresponding parts (e.g., part01 through part08) and then use a file extraction tool like WinRAR or 7-Zip to unpack them.