To add visual search functionality to your search center, first of all, please make sure that the Ontolica Preview for Search feature is activated in the Site Actions > Site Settings > Site collection features. That will make the Ontolica Preview for Search Web Part available for that site collection. Then please go to the search result page of your search center, where you want to add the Web Part and select Site Actions > Edit Page option. While in the edit mode, click Add a Web Part link on any Web part zone. Locate the Ontolica Preview folder under the Categories column, select the Ontolica Preview for Search Web Part under the Web Parts column and then click the Add button. Note: first-pagepreview images of documents will not be available until the Ontolica Gatherer service processes documents in question.