If you want an object to show in more than one place, use the location option http://ez.no/doc/ez_publish/user_manual/3_8/daily_tasks/publishing_at_multiple_locations
If you are in a template, you can show any object by first fetching the node_id you want. Although the more you learn about ezpublish you may change your mind as to how to structure your node tree.
Take a look at the template fetch functions within the documentation under http://ez.no/doc/ez_publish/technical_manual/3_8/reference/modules/content/fetch_functions/list
