You can create a Table of Contents by applying heading styles. Like Heading 1, Heading 2 etc. to the text to include in the Table of Contents. Word searches for those headings and then inserts the Table of Contents into your document. When you create the Table of Contents this way you can automatically update it if you make changes in your document.
Do the following to create a Table of Contents
First of all apply a "Heading Style" to the text that you want to be included in the Table of Contents. Then later you can use these headings to update your Table of Contents.
Click where you want to insert the Table of Contents.
Now click on the "Reference" Tab.
Choose "Table of Contents" that shows a pop up where you can select an automatic table from the gallery of styles.
Note: you can also select the manual table that Word will automatically add placeholder text to help to create a design of the Table of Contents.
When you choose manual Table of Contents then that will be updated automatically.
To update a Table of Contents do the following.
Click on the "Reference" tab and choose "Update table".
Now you can choose to update all of your Table of Contents or only update the page numbers.