An Aspect Ratio is basically the ratio between the width and height of your display. While there are many different aspect ratios out there, the most common ones include 16:9 (Widescreen), 4:3 (Fullscreen) and 21:9 (Cinemascope). HDTV's are generally formatted in widescreen format to display high-definition images, so it is important to select the right aspect ratio so that you can display images properly on your TV.
Turn on your TV. Aim the remote control towards the TV and press the "Menu" button. If you do not have a remote, press the "menu" button on the TV. Depending on the TV model that you are using, the menu button is generally located on the front or back of your TV.
Press the arrow buttons on your remote control or TV and select your display options. The display options vary with different TV models, so refer to your TVs operating manual. From the display options select "Aspect Ratio." Select the aspect ratio that you want to use. Select 16:9 if you want to display your images in a widescreen format. Select 4:3 if you want to display your images in a full screen format. Although HDTV's are generally formatted in widescreen format, you can use other formats such as fullscreen. Press "Exit" or the "Menu" button on your remote controller or TV to exit the menu.
Press the "Aspect Ratio" button on your remote controller repeatedly until you select the aspect ratio that you want to use. Use this as an alternative to step two. Some TV remotes have a one-press button that you can use to change the aspect ration. If your remote controller does not have an aspect ratio button, use the main menu to select the aspect ratio you want use.