Open the Settings app
To start with, tap on the Settings app of your phone – this is the one with a cog symbol.
Tap on Wallpaper and Style
Once you’re in the Settings app, scroll down and tap on the option saying Wallpaper and Style.
Select My Wallpapers to choose from a selection of pre-installed options
With this menu open, you’ve got a couple of choices. If you want to browse the range of pre-installed wallpaper options from Samsung then you can tap on My Wallpapers.
Tap on Gallery to choose an image that you have taken or downloaded
Alternatively, in the Wallpaper and Style menu you can tap on Gallery in order to choose an image that you’ve already downloaded, saved, or snapped with your camera.
Choose to use the wallpaper as your Lock Screen, Home Screen, or both
Once you’ve made your choice, you’ll be asked whether you’d like to use the wallpaper as your Lock Screen, Home Screen, or both. The Lock Screen is the one that appears on your phone before you have entered your PIN, pattern, or used biometrics; the Home Screen is the one that appears afterwards and is the background for your main menu of apps.