The way to begin the next part of your text on a new page is to enter a hard page break. You do this by pressing Control+Enter. Duxbury will not preserve this in your Braille document unless you set the Word Importer to do so; generally, you will not want to preserve hard page breaks, unless you are beginning a new Chapter in a book.
So if you have another column of paragraph marks (remember the button to click?), backspace them into oblivion and press Control+Enter. You will then see a nice clean page break: