Janice - welcome to the world of RapidWeaver, and Macs!
Although you may be able to bring the text, images (by copying and pasting them) and some of the layout to RW, it's entirely its own system and it's not possible to 'import' any code from other sites.
When you say a 'web page', if you do mean just one single page, it won't take you more than an hour or two to build an equivalent in RW… certainly less time than trying to 'convert' it.
Once you've made the jump, though - perhaps following one of the many Getting Started 'courses' available - I think you'll find RW a flexible, robust and well-supported tool to become familiar with. Good luck - and do share your results here, please