1.) On the Tools menu, click Templates and Add-ins.
2.) Click Linked CSS.
3.) Click Add.
4.) Select the cascading style sheet (CSS) you want to add, and then click OK.
5.) Repeat steps 3 and 4 to attach more style sheets, or click OK if you are finished.
The styles from the cascading style sheet will appear in the Styles and Formatting task pane.