functions.php

<?php

searchwp_modal_form_trigger( array(
	'echo'     => true,                 // Whether to echo
	'type'     => 'button',             // Either 'link' or 'button'
	'text'     => 'Open Search',        // Text of the trigger
	'engine'   => 'my_searchwp_engine', // SearchWP engine (when applicable)
	'template' => 'My Custom Template', // Modal template to use (see docs)
	'class'    => array(),
) );