From a Home screen, navigate: Apps icon > Gallery. If Gallery is unavailable, tap the Dropdown menu (located in the upper-left) then select Alphabetical. If still unavailable, refer to Manage App Icons.
Locate then tap the preferred image.
Tap the Menu icon (located in the upper-right). If necessary, tap the screen to display the options.
Tap Set as.
Tap Contact icon.
Tap the desired contact.
If presented, position the crop frame over the desired area of the picture then tap DONE.