Select from category

The plugin was not written to filter your results by catagory but you could hack the index.php file to alter the WP_Query.

Right before line 96 $SMALY_query = new WP_Query($arr);
you could add your parameter to the $arr array, like this:
$arr['cat'] = 4;
or
$arr['category_name'] = 'staff';
or
$arr['category__in'] = array( 4, 5 );

You can get some more advanced usage ideas here:
https://codex.www.ads-software.com/Class_Reference/WP_Query#Category_Parameters