1) Open Scrapbook Max
2) Open a New Page
3) Go to Page > Settings > Size > set width to 16 and height to 8 (inches)
4) Bring in your published page (drop & drag or bring in as an embellishment)
5) Decide which side you wish this page to be (left or right)
6) Stretch to cover the whole side of half page
It's exactly how I would have done :-)
or I would have choose another option in doing directly the 2 pages on the same page :-) as I work in px: 7200 x 3600 (size of the page).