To include one page within another we use a syntax similar to what was used with Dreamweaver on Frontier:
Make sure you are in HTML mode (have the "Editor" selector set to HTML) when pasting this in. This directive will include the contents of the page you've created on your site at http://yoursite.unl.edu/some/path in the spot you include this directive.
It also can be used to include a page from another site at a different domain:
The referenced page needs to either be a page from a UNLcms website or it needs to be a partial HTML sippet that is not wrapped in a web template.