First let me say that I'm new to web design..... I have an existing HTML web site that I'm trying to maintain for an organization that I belong to. Is there any way to convert it from HTML to VNU so that I can use the visual design software? I don't know HTML, so it would take a lot more effort for me to learn the language if I go that route.

No, you have to rebuild the site in VSD.

I guess rebuilding is the only option you have, and you will learn it quickly, you just dont need to lose heart, nothing is difficult, you can do it easily once you start doing it. Even I was once a beginner learner like u and now I have build the skill, I wish u best of luck for it.

You can save your original site's images and graphics to be inserted into your VSD site, also, you can copy text and paste it into your VSD pages (I would paste it to notepad first to get rid of formatting).

If you get your new site set up with backgrounds, menus, etc. in place; inserting the content and images goes pretty quick.