You can do a subject search even if you don't know what subject heading(s) are used to describe your topic. All you have to do is find one really good item on your topic and look at its subject headings.
A good strategy is:
For example, a keyword search on native american and art might retrieve the following item.
Note that the keyword native american was only found in the title and not in the subject heading. Clicking on the linked subject heading will retrieve other items with the same subject heading.