The default search engine that ships with WordPress does not do a very good job when you start to get a bit of content on your WordPress powered site. It just isn’t as smart as Google search so you should integrate Google Custom Search (CSE) into your WordPress site as sooon as possible. This will allow your visitors to searh your site efficeintly.
In this video tutorial I will show you how you can easily change your default WordPress search to use Google Custom Search without using any WordPress plugin(s).
Integrate Google Custom Search into WordPress Video
Alternatively, you can view this video on YouTube by going to the following link
Now you should be all set to let your visitors search your site using Google search.