In WordPress there’s a feature image box in post edit screen. However this feature is theme dependent and is called post thumbnails. It’s a new feature introduced in V2.9 and is enabled through add_theme_support().
This post demonstrates the most basic way to enable and display a feature image.
Add the following code to
add_theme_support( 'post-thumbnails' );
Feature image meta box will show up on the right side of post edit screen. Simply click ‘set feature image’ and follow instruction to add / select a feature image.
To show the feature image in your theme, add the code to the template (within the loop):
if (has_post_thumbnail()) the_post_thumbnail();
the_post_thumbnail() directly displays a preformatted <img> code.