I am trying to make the search bar on my SharePoint page search both a wiki library and previous posts on a discussion board. The page I am working on is a resource center, so I want users to be able to search one place and get aggregated results of our two resources; wiki pages and a discussion board. I haven't been able to find any other posts or sites explaining how to do this and I am at a loss. Any help would be appreciated!
I would begin by creating a Result Source for your specific content. Then create a search page (just a web part page with Search Web parts on it.) Bind the Results Web part query to your new result source. Add a search box to your page and send the query result to your new results page.
If you are not clear on the exact steps I recommend you watch my play list here: Create a Search Based Site Directory It's not exactly what you are doing but contains many of the elements.