The 'import' element occurs at the top level.

Example:

<xs:import namespace="urn:publicid:IDN+cde.berkeley.edu:schemas:something:us" 
           schemaLocation="something.xsd"/>
<xs:import namespace="http://www.w3.org/1999/xhtml" 
           schemaLocation="xhtml.xsd"/>

The 'namespace' attribute specifies what namespace you are attempting to import.

The 'schemaLocation' attribute is not required, but recommended.

You still have to define a prefix to refer to definitions/declarations.