Press the “Safari” icon to launch the iPhone Safari browser.
Go to the images section of any search engine within the iPhone Safari browser. Type in “black wallpaper” and click on the first black wallpaper image that appears. Press on the image for a few seconds until you are prompted to save it. Press “Save Image.”
Go to the main iPhone screen and press “Settings.”
Select “Desktop Background” to change this wallpaper.
Press “Camera Roll.”
Press the black image you just downloaded and select “Set” to make your iPhone’s desktop background black. Repeat the process to select this image as your iPhone’s lock screen background if desired.