You can offer YouTube video search functionality to your site visitors by including "Video Search" widget on your sidebar.
To accomplish this task:
Go to Appearance menu after logging into WordPress dashboard.
Click on Widgets submenu link.
Drag and drop "Video Search" widget to one of the sidebars available in your theme. Remember if you move the "Video Search" widget to "EMD Widget Area", it will show only in the YouTube ShowCase video pages.