This article explains how to replace the native search bar in the XStore theme by 8theme.
FiboSearch plugin features built-in integration with this theme. It means you can replace the default search bars by selecting a single checkbox.
If you have activated the XStore theme or the child theme of XStore theme, you should see the following screen in the plugin settings:
WooCommerce → FiboSearch → Starting (tab)
Select the option Replace all XStore search bars with FiboSearch and the search bar should be replaced.