You need to register and create a sidebar in the place you need the widget

Register in functions.php

register_sidebar(array(

  'name' => 'HeaderSideBar',

  'id' => 'header-sidebar',

  'description' => 'Widgets in this area will be shown on the header.',

  'before_title' => '<h1>',

  'after_title' => '</h1>'

));

Add the place in header.php

dynamic_sidebar('sidebar_header')

Then assign the widget to the sidebar