You can't force a page break manually while writing but you can either choose a different layout template that already has a page break associated with a particular element (such as an act start in a TV template) or create the association yourself.

To do this go to Format > Elements then choose an element such as General and check the​​​​ "Start New Page" box for that element.

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Then when you return to your script you can select that element at the start of the paragraph in which you would like to start a new page.