I am not familiar with CubeCart3 but in order to embed a SimpleViewer gallery in a web page you will need to be able to do the following:
(1) Upload the gallery folder to a web server.
(2) Insert HTML embedding code into the web page.
I do not know if CubeCart3 allow you to do either. Please check with their support.

If CubeCart3 do not provide web space and the ability to upload files and folders via FTP, then you would need to find a suitable host for your SimpleViewer gallery. One such host would be Dropbox.

In order to upload SimpleViewer gallery to Dropbox, follow these instructions:
(1) Download and install the Dropbox client program from this web page
(2) Run the install program and sign up for a free Dropbox account
(3) Create your SimpleViewer gallery with the method of your choice (such as svBuilder)
(4) Drag and drop the entire gallery folder into the 'Public' folder within the newly created Dropbox folder on your computer
(5) Navigate towards your gallery's 'index.html' file (within 'username/Dropbox/Public/gallery_folder/'), right-click it and select 'Dropbox -> Copy public link'

Now, assuming CubeCart3 allows you to add HTML to your web page, all you would need to do to embed the gallery is to insert a single line of HTML code, an <iframe> whose 'src' attribute points towards the 'index.html' page within the gallery folder (the URL you copied in Step #5 above).
The <iframe> would look like the following:

<iframe src="Dropbox_URL_Goes_Here" width="800" height="600" frameborder="0" scrolling="no"></iframe>