How do I set my new 4K or Ultrawide wallpaper?

Windows 11: Right-click your desktop and select Personalize > Background. Click Browse photos to select your downloaded file. For Ultrawide monitors, ensure "Choose a fit" is set to Fill or Span to avoid black bars.
macOS (Sequoia): Right-click your desktop and select Change Wallpaper. Click Add Photo (or the + icon) to find your download.
Mobile: Open the image in your Photos app, tap the Share icon, and select Use as Wallpaper. Pinch to zoom and align the samurai to your liking.