This is the search box that appears on the Yale University Library home page. Use Quicksearch and enter search terms in the box to get started searching. Don't worry about being too precise at first; you can easily narrow down your results later by clicking on the results and using the choices on the left hand side.
In your results screen, you'll notice that there is a Books+ column on the left, and an Articles+ column on the right, with "View and filter all...results." Click on the "View and filter..." which will take you into a new screen where you can filter down the many results you get using options (facets) on the left. Many of the articles in the Articles+ results are fully available online to the Yale community.