Adding a Search Form In The Header
Go to WP Admin > Appearance > Widgets and drop a "Search form" widget on one of your sidebars.
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".
Make room for the search form. Using the "Columns selector", reduce the columns size of the modules used in the header.
Drop the "Widget (Sidebars)" module.
By default, a module will have 12/12 column width. Select the 1/12 column width.
Move the module on the right side of the menu.
Open the "Widget (Sidebar)" module settings panel and select the sidebar where you dropped the search form widget.
Style the module to fit it nicely in the header.
Publish the changes.