Open System Preferences and click Appearance.

Choose a font smoothing style from the pop-up menu at the bottom.

Depending on the type of display you have, you may notice only small or no differences between smoothing styles.

If you plan to use small font sizes in your document, choose a point size from the “Turn off text smoothing for font sizes” pop-up menu.

When text smoothing (or antialiasing) is on, smaller fonts can be harder to read.