You will need to activate the Ontolica Preview for Aggregate feature in the site collection features list to be able to add the Web part to an Ontolica Aggregate Center. Then go to your Ontolica Aggregate Center and select Site Actions > Edit Page option. Locate the Ontolica Preview folder under the Categories column, select the Ontolica Preview for Aggregate Web Part under the Web Parts column and then click the Add button. A column with a small magnifier image (default) for each row will be added to the existing list of columns in the Ontolica Aggregate Center. The color of the magnifier icon for a document will be grey until it gets crawled by the Ontolica Preview Gatherer service and its color gets changed to blue after it is crawled. In the Ontolica Preview configuration pages the magnifier image can be replaced by a small thumbnail image of an actual document. Please note that even if the default magnifier icon has been changed to the small thumbnail image you will see the magnifier icon before the document in question gets crawled by the Ontolica Preview Gatherer service. Placing the mouse over the magnifier/thumbnail will display the first-page-preview image of a document/page and clicking that image will show full-document-preview images for that document/page. To close the pane with full document preview images you need to click the magnifier/thumbnail preview image again.