To change the level of an entry in your table of contents, just change the heading level of that text in the body of your document.
Click the heading that you want to change.
On the Home tab, in the Styles group, click the heading level you want.
On the References tab, click Update Table.
Click Update entire table, and then click OK.
Word automatically includes the top three levels in a table of contents. For more or fewer levels, see Change the levels in a table of contents.