Content approval and publishing is contained within Workflow topics.
More information on transitioning items/approving them can be found at http://help.percussion.com/publishing… .
The reason that an asset is not appearing on the page is likely to do with the fact that the asset hasn’t been approved. You will have to go back to that specific asset and edit it and then approve it. Once it has been approved, re-publish the page that you were working on and it should appear.