You can call add_image_size in your functions.php:
add_image_size( 'medium', 240, 160, true );
Reference here:
http://codex.wordpress.org/Function_Reference/add_image_size
You can call add_image_size in your functions.php:
add_image_size( 'medium', 240, 160, true );
Reference here:
http://codex.wordpress.org/Function_Reference/add_image_size