You can search for specific songs anywhere in app by tapping on the search field.
Write a song name or artist name you want to find and hit enter/tap done. This will give you a list of results that match your initial search criteria. If you'd like to add filters to your search, simply tap/click on Filters in the top right hand corner.
You can then add filters by dragging the circles to filter songs by difficulty level.
Clicking the back arrow will reset the search and you can change the search filters by clicking/tapping on the Filters options.