At some point you may decide that the formatting of an existing style is close to but not exactly what you want. You do not need to create a new style; modify the existing one.
Open a document containing the style you want to change.
Click to display the Styles and Formatting task pane.
The Styles and Formatting task pane appears.
Place over the style you want to change. appears.
Click to display a list of options.
Click Modify.
The Modify Style dialog box appears.
Select any font formatting or paragraph formatting changes you want to make.
Click the Add to template option to make the modified style available in new documents ( changes to ).
Click OK.
Word changes all text formatted with the style to incorporate the changes.
What does the Style based on option do?
Every style you create is based on a built-in Word style. Changing a built-in style can result in many styles changing. For example, many styles are based on the Normal style. If you change the font of the Normal style, you change the font of all styles based on the Normal style.
What does the Automatically update option in the Modify Style dialog box do?
This option ( changes to ), available only for paragraph styles, causes Word to change a style definition if you apply manual formatting to a paragraph assigned to this style. Because you may not realize that Word is changing the style’s definition, this option is recommended or experienced users only.