I have a little problem... when I want to show the featured image on my posts, the chosen size isn\'t working (the photo is shown in it\'s own size). And I want the featured
Put this code add_theme_support( 'post-thumbnails' ); in function.php file
Put the php code add_theme_support( 'post-thumbnails' ); on functions.php under the theme directory.
WordPress cutting thumbnails while uploading the file, so you have to enable the feature first then upload the image.
Select Post option,at right side bar corner,you will find the option as Featured images changes and updates,select and update the image which you require.
Else try with this Code format: the_post_thumbnail(); set_post_thumbnail_size( 50, 50);`add_image_size( 'single-post-thumbnail', 590, 180 );