After you have set up a content repository, you can use it to serve targeted content, as described in the Creating Rules for Targeting Content and Setting Up Targeting Services chapters of the ATG Personalization Programming Guide. You can also search for text in content items as described in the Text Search Queries section of the SQL Repository Queries chapter.
You can also get repository items programmatically, given a repository ID:
// repository id of the item we want to get String id = "1001"; // name of item descriptor describing the type of item we want String descriptorName = "book"; // get the item from the repository RepositoryItem item = pRepository.getItem(id, descriptorName); // make sure we have an item if (item == null) { pln("Item not found, descriptor=" + descriptorName + ", id=" + id); return; } // get the author property of the item String author = (String)item.getPropertyValue("author");