Press and hold the blank area on your screen (the blank space where no icons/apps are placed). As and when you press the screen, the home screen option appears.
Pick the ‘add wallpaper’ option and select whether you want the wallpaper to appear on the ‘Lock Screen,’ ‘Home Screen,’ or ‘Home & Lock Screen.’
You will also have another set of options appearing in front of you for the selection of wallpaper from locations like — Gallery, Wallpapers, Live Wallpapers, or Photos.
If your wallpaper is in the Gallery, pick the option. You can also crop the image to match the size. Once you are satisfied, tap on the ‘Done’ option.