I am not familiar with Business Catalyst but if you split up the process of embedding a SimpleViewer gallery into its component parts, it involves uploading a folder and pasting a section of HTML code into a page.
You could upload the entire gallery folder (not just its contents) and use one of the two methods of embedding documented here.

It might help to not think of it as trying to embed a SimpleViewer gallery and the two processes that you would need to figure out would be:
(1) How to upload a folder (containing files and subfolders) to your web server from within Business Catalyst, and...
(2) How to insert HTML code into a page using Business Catalyst

Perhaps someone familiar with Business Catalyst (or the Business Catalyst forum or support pages) could help further with this.