Click Design, then Paragraph Spacing. Pick which spacing you want (the default is Open), and notice your whole document will preview as you mouse over the different settings.
If you don’t like those options, click Custom Paragraph Spacing and change the numbers under Paragraph Spacing.
Don’t want to change the spacing in the whole document?
Click anywhere in the paragraph you want to change.
Go to Layout, and under Spacing, click the up or down arrows to adjust the distance before or after the paragraph. You can also type a number directly.