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Actually, the idea of a content management system is to use the system to manage the content you add to your site.
If you want to do it without using a module, make a custom block and add the link to the page(s) you want to add.
You could also hack the Main Menu block to add your content. But it will appear either above or below the existing links.
There are plenty of modules on XOOPS that can be used to add content and/or create a pagewrap around a pre-made page. But if you don't want to use a module, I don't really know if there is really much anyone can do. Maybe HTML will work better for you.