If you do not see the "Action Item" type, you may need to check your SearchableTypes.properties file and make sure it is listed there. If not, use the .xconf file to make the update at <WT_HOME>\codebase\com\ptc\windchill\enterprise\search\server\SearchableTypes.properties.xconf and then propagate the necessary changes.
Check the line that starts with "ProjectLink.allSearch=" in the .properties file. If you do not see it there, you can update the line in the .xconf file that starts with "<Property name="ProjectLink.allSearch" multivalued="," default="wt.part.WTPart, ... " and include the internal name of the object type (likely is wt.meeting.actionitem.DiscreteActionItem). Then, propagate the changes.
Feel free to contact me if you have any other questions - you can reach me at robert.sindelar@eccellent.com