It's easy guys, follow the steps
Go to settings , select display, wallpaper
By default it opens theme centre
In theme centre click camera icon ( that is photos from gallery ) select your image, crop image if required. Select the tick mark on top.
It shows three options for setting your image as wallpaper, select your options as wallpaper. Enjoy!! Hope you got your answer.
There is lock screen option in the theme setting. Give lock screen change option details
Enable your Theme center app.
Go to Setting -> Apps -> Theme Center -> enable the app. Now you can change your lock screen wallpaper :-)
But when i click on wallpaper as you said i got an error message of unfortunately setting has been stopped. Everytime
i follow your answer but when i open sttting > display > i show message (Unfortunately, settings has stoped)
so what can i do ??