Field Searches --You may designate if you want to search anywhere in the record (Select a Field (optional)), only the title, only the author, only the subject, etc., by changing the default fields. (See screen shot below.)
Once you have executed a search, MLA suggests subject terms along the left-hand side of the results (under Subject) which you can AND with your original search to focus your search or substitute for your original search term(s). If you want to AND a term with your original search, just check the box next to the term you want to AND into your search and then click on Update.
You can also limit your results to the Source Type (journal articles, book articles, dissertations, etc.) by clicking on a specific type in the left-hand side bar.