You will want to use a keyword search, in Discover, to find scores. Some possibilities include the uniform title, the instrument, the type of work (concerto, opera, quartet, symphony, etc.), the composer, any numbers associated with the composer (like the Mozart's catalog numbers like k 626), and more. Be creative.
You can search Discover or the Library Catalog for scores. The example, below, shows a search in Discover.
Steps to Locate Scores