To enter a query, just type in a few descriptive words and hit the 'enter' key (or click on the Search button) for a list of relevant entries. Refining or narrowing your search is as simple as adding more words to the search terms you have already entered. Your new query will return a smaller subset of the documents found for your original "too-broad" query.
By default, the database only returns items that include all of your search terms, not necessarily as a phrase. Keep in mind that the order in which the terms are typed will not affect the search results.