Fields in User Profile Page

For a quick solution put this code in functions.php of your theme:

add_action( 'show_user_profile', 'show_extra_profile_fields', 10 );
add_action( 'edit_user_profile', 'show_extra_profile_fields', 10 );

function show_extra_profile_fields( $user ) { ?>
    <input type="text" name="twitter" value="<?php echo esc_attr( get_the_author_meta( 'twitter', $user->ID ) ); ?>" />
<?php }

Or you could do it with a plugin: http://www.cozmoslabs.com/wordpress-profile-builder/