For lengthy Word documents, such as reports, theses, or articles, it's essential to create an automatic table of contents. An automatic table of contents not only helps you summarize the main contents but also makes it easy to navigate to the content you want to view. If you're unfamiliar with how to create an automatic table of contents in Word, check out the following tutorial.

Below is a guide on how to create an automatic table of contents in Word 2016. The process is similar for Word 2007, 2010, and 2013.
Creating Headings in Word
By using headings, you can easily create a table of contents and manage your Word documents. First, you need to format the headings:
In the Home tab, under the Styles section, choose the expand icon next to Styles or press Alt + Ctrl + Shift + S.

You only need to use Heading 1 through Heading 6 depending on the levels in your Word 2016 document. Other Styles can be hidden on the Styles pane by hovering over the right side of the style name, clicking the inverted triangle icon, and selecting Remove from Style Gallery.

If your Styles menu doesn't display from Heading 1 to Heading 6, click the icon below to open Manage Styles.

Here, select the Recommend tab, then choose from Heading 1 to Heading 6 and click Show, then select OK.
Note: During the heading creation process, if you only want to create headings for the current Word document, select Only in this document. If you want to create headings for all future Word documents based on this template, select New documents based on this template.

Now, in the Styles dialog box, all the selected Headings are displayed. Next, you need to format each Heading.
Formatting Headings in Word
Below, we'll guide you through formatting one Heading, and you can format subsequent Headings similarly. Note that you can format however you prefer, but for a more polished and cohesive Word document, it's advisable to establish a uniform formatting for Headings.
First, click the inverted triangle icon next to the Heading name (e.g., formatting for Heading 1) -> Modify.

The Modify Style window appears, where you can select font, font size, font style, font color, alignment, etc., under the Formatting section.

To format Paragraph, select Format -> Paragraph.

The Paragraph window appears where you adjust the Spacing section, setting the space before, after, and line spacing according to your document. Once configured, click OK to close the Paragraph window, then OK again to close Modify Style.

Continue formatting subsequent Headings in a similar manner.

Adding Headings to Sections in Word
First, press Ctrl + F to open the Navigation pane. In the Headings tab, you'll clearly see the headings when you add sections.

For major sections like I, II, III..., use Heading 1; for subsections like 1.1, 1.2, 1.3..., use Heading 2; for sub-subsections like 1.1.1, 1.1.2, 1.1.3..., use Heading 3,...
Adding Headings is done by clicking on the section you want to add, for example, “CHAPTER I...”, then selecting Heading 1 from the Styles in the Home tab. Alternatively, you can choose Heading 1 directly from the Styles table you've just configured.

Wherever you perform an action, it reflects in the Headings section of the Navigation pane. For instance, for section 1.1, select Heading 2. Similarly, click on line 1.1 and choose Heading 2. The Navigation pane will display the newly added Heading 2.

Similarly, scroll through the text and add Headings to all sections of the Word document.

Numbering Pages in Word Documents
Select Insert -> Page Number -> choose position and numbering format.

If you want to number pages starting from any page, refer to the detailed guide here.
Creating Automatic Table of Contents in Word
After adding Headings and numbering pages, proceed to create an automatic table of contents by placing the cursor on the page where you want it, then go to References -> Table of Contents -> choose a template for automatic table of contents (if you want to create a custom style, choose Custom Table of Contents).

The table of contents will be generated based on the headings you've set.

To remove the automatic table of contents, select the table of contents, click on the icon as shown below, and choose Remove Table of Contents (or go to References -> Table of Contents -> Remove Table of Contents).

If you want to update the table of contents because you've changed the page order of the sections while editing, select the entire table of contents and click Update Table (or go to References -> Update Table under Table of Contents).

To navigate to the desired content, simply press Ctrl + click on the table of contents entry you want to view, and Word will automatically scroll to the page containing the selected section. If this doesn't work, you need to adjust settings in Word Options as follows:
Select File -> Options.

In Word Options -> Advanced -> check the box next to Use CTRL + Click to follow hyperlink, then click OK to save.

So you've successfully created a table of contents in Word 2016 using headings. If you prefer not to use headings, you can explore alternative methods for creating an automatic table of contents here.
Wishing you all the best of luck!
