which device are you using as source? Should be adjustable in this one
other than that the TV has settings for such as well:
Press the HOME button, then select [Settings] — [Picture & Display]
Screen
Adjust the aspect ratio and viewable screen area.
Wide mode: Adjust the picture size.
Auto wide: Automatically adjusts wide mode based on the signal.
4:3 default: Automatic sizing for 4:3 pictures.
Auto display area: Automatically adjusts the viewable screen area based on the signal.
Display area: Adjust the viewable screen area.
Screen position: Adjust the vertical and horizontal screen position.