Apply built-in heading styles to the text you want included
Place the cursor where you want the table of contents
Go to the References tab
Select Table of Contents
Choose an automatic table of contents style
To add new entries, apply heading styles to the new sections
Click inside the table of contents
Select Update Table
Choose Update entire table
Click OK
To customize entries, use the Table of Contents menu
Select Custom Table of Contents if needed
Adjust levels, formats, and tab leaders
Click OK to insert or update the table of contents