This plugin gives a very simple way to integrate Google Search into your WordPress site.
If you would like a Google search feature on your WordPress site, you only need to register to Google Custom Search, get your Google Search Engine ID, and enter it in the plugin settings page.
Then your Google custom search engine is ready for use, just put the new Google search-box widget on the sidebar, and enjoy it! In this way the plugin enables you to insert Google search engine into your website, or a collection of websites easily. You can search both web pages and images. You can define if you want to search only inside your site (or given sites), or the entire web.
It is possible to customize your search features, the look and feel (layout, themes, custom colors and fonts, thumbnails), and many more. All these settings can be specified on the Google Custom Search Engine admin site: https://www.google.com/cse/ Your changes will appear instantly on your site automatically.
After you registered to Google Custom Search Engine and get your Google Search Engine ID, you need to enter the ID in the plugin settings page: Settings -> WP Google Search Use WP Google Search widget or [wp_google_searchbox] shortcode to place search box on your site.
Search results can be displayed on a normal page or in a popup window. Use Full Width layout or Overlay (popup) layout on Google Custom Search Admin site to setup it.
It does not require any coding, or other complicated operation.