adding custom widget (signup form) to the header

Hi! I am trying to add a custom signup form to the header (logo left, menu below) and hoping for help with 2 quick things:
1) I read a thread of your blog with code to add to php and custom css to add a custom widget area to header:
add_action( ‘ava_after_main_menu’, ‘enfold_customization_header_widget_area’ );
function enfold_customization_header_widget_area() {
dynamic_sidebar( ‘header’ );
}

and custom quick css:
#header .widget {
left: 50%;
padding-top: 0;
position: absolute;
top: 0;
transform: translate(-50%) !important;
}
and added widgets to the “header widget” but nothing is showing up. Is there an ammended code fix to get this to work?

2. Is there a way to make the widget fluid, responsive?
3. Is there also a quick css fix to center the menu below (vs.displaying to the left) ?

Thanks in advance for your help, love the theme!

~ Sophia