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Adding a Search Form In The Header

1

Go to WP Admin > Appearance > Widgets and drop a "Search form" widget on one of your sidebars. 
2
Go to WP Admin > Appearance > Headers/Footers and select the header you are using. In the case you are using the demo content, open in Live Composer the "Header - default design".
3
Make room for the search form. Using the "Columns selector", reduce the columns size of the modules used in the header.
4
Drop the "Widget (Sidebars)" module. 
5

By default, a module will have 12/12 column width. Select the 1/12 column width.

6
Move the module on the right side of the menu.
7
Open the "Widget (Sidebar)" module settings panel and select the sidebar where you dropped the search form widget. 
8
Style the module to fit it nicely in the header. 
9
Publish the changes.