Automatically generate a table of contents for articles in word

Automatically generate a table of contents for the articles in word: if the

title format in the article is the

first section...big title (level 1)
1.1...subtitle (level 2)
1.1.1—...subtitle under the subtitle (level 3 ) )
…
Section N…major title (level 1)
n.1…subtitle (level 2)
n.1.1—…subtitle under subtitle (level 3)

Automatically generate article table of contents:

1. To set the title format

1. Select all the first-level titles in the article;
2. On the left end of the "Format" toolbar, click "Title 1" in the "Style" list.
Follow steps 1 and 2 to set the second and third level heading formats as heading 2 and heading 3.