1. Signup for the  Google Custom Search service at  https://cse.google.com/cse/ . It's free.   When you set up the custom search feature, fill in your podbean site URL, such as http://slug.podbean.com,  as the site to search.  

2.  Get the embed code from google custom search.

3.  From your Podcast Dashboard, go to Layout->Sidebar Widgets to add a "Text" widget on your sidebar.  Edit the widget by pasting in the google search embed code. Click "Save Changes" on the Sidebar widgets page.