Add search functionality to my new WP 4.4 site
I'm brand new to WP, using 4.4, and am using the Divi Builder from Elegant Themes. I disabled their header, to use my own custom-designed header and menu. How do I add in a Search functionality? I found Relevanssi in the WP Plug-Ins, but I'm such a novice, I'm not sure how to create the Search box (similar to the top right of this page). Also not sure if Relevanssi is the best option to use. The default Search on the Divi Theme took the search results to a WP page with a Sidebar showing things related to a blog. My site isn't a blog, so I don't want that Sidebar there; just the Search results. Thank you!