Add NGram analysis to Sunspot

1-sunspot-schema-plus-ngram.xml

<?xml version="1.0"?>
<schema>

  <types>

    <fieldType name="text" class="solr.TextField" omitNorms="false">
      <analyzer>
        <tokenizer class="solr.StandardTokenizerFactory"/>
        <filter class="solr.StandardFilterFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
      </analyzer>
    </fieldType>

    <fieldType name="text_ngram" class="solr.TextField" omitNorms="false">
      <analyzer>
        <tokenizer class="solr.StandardTokenizerFactory"/>
        <filter class="solr.StandardFilterFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
        <filter class="solr.EdgeNGramFilterFactory" minGramSize="1" maxGramSize="6" side="front"/>
      </analyzer>
    </fieldType>

    <!-- ... -->

  </types>

  <fields>

    <!-- ... -->

    <dynamicField name="*_text_ngram" type="text_ngram" stored="false" multiValued="true" indexed="true"/>

    <!-- ... -->

  </fields>

</schema>

2-sunspot-searchable-with-ngram.rb

class Article < ActiveRecord::Base
  searchable do 
    text :firstname # creates firstname_text field
    text :firstname, :as => 'firstname_text_ngram'
  end
end

where put this code??
thanks.