On the References tab of the Ribbon click Table of Contents > Custom Table of Contents.
In the Table of Contents dialog box, click Modify. If the Modify button is grayed out, change Formats to From template.
Use the Table of Contents dialog box to customize the appearance of your table of contents.
In the Styles list, click the level that you want to change and then click Modify.
The Modify Style dialog lets you update how the text in your table of contents will look.
In the Modify Style dialog box, make the formatting changes that you want, and then click OK.
Repeat steps 3 and 4 for all the levels that you want to display in your table of contents.