Hi @pannlann,
Another approach is to save a new file named searchform.php to your child theme’s directory. Any code that you add to this file will be used in place of the default search box.
Add the following to the file:
<form role="search" method="get" class="search-form" action="<?php echo home_url( '/' ); ?>">
<label>
<span class="screen-reader-text"><?php echo _x( 'Search for:', 'label' ) ?></span>
<input type="search" class="search-field"
placeholder="<?php echo esc_attr_x( 'Example …', 'placeholder' ) ?>"
value="<?php echo get_search_query() ?>" name="s"
title="<?php echo esc_attr_x( 'Search for:', 'label' ) ?>" />
</label>
<input type="submit" class="search-submit"
value="<?php echo esc_attr_x( 'Search', 'submit button' ) ?>" />
</form>
The following part of the above code defines the placeholder text:
placeholder="<?php echo esc_attr_x( 'Example …', 'placeholder' ) ?>"
Change Example to the specific text you wish to use.
Let us know how you get on with that!