Drag the template from the templates pane on to the first video/image on the timeline, the same procedure is also used on the last video/image for Outro's if you are going to use one.
However you cannot add an Intro and Outro to a single video clip - they must be applied to separate objects, if the video is one long video then make a cut in it to create 2 video objects - the cut will not affect the rendered export..