Hitting Return or Enter places blank paragraphs in your script that can affect pagination later when you make revisions. Don't do it.
Instead, change the number of blank lines before the paragraph. To do this, place your cursor in the paragraph you want to move down the page, go to Format > Space Before and choose the number of blank spaces you want. This will move the paragraph down the page appropriately.
If you need more than a 3-line space, choose Other... and type in the number of lines you need.
If you need a certain number of spaces between scenes throughout the script, go to Format > Elements Settings (Windows) or Format > Elements (Mac), click Scene Heading from the list on the left and click the Paragraph tab. Change the Space Before to the number you need.