Final answer:
To create a heading in Word, position the cursor, select a heading style from the 'Styles' pane in the 'Home' tab, and customize it using 'Font' options. Add a line beneath by choosing 'Bottom Border' in the 'Paragraph' group.
Step-by-step explanation:
To insert a heading line in Microsoft Word, you first need to position your cursor where you would like the heading to appear. Then, go to the 'Home' tab on the ribbon at the top of Word and find the 'Styles' pane. You can choose one of the pre-set heading styles, such as 'Heading 1' for a main heading, or 'Heading 2' for a subheading. Clicking on one of these will apply the heading style to your text.
If you want to customize your heading further, you can highlight your heading text and then adjust the font type, size, and color using the options within the 'Font' group of the 'Home' tab. To add a line beneath your heading, you can use the 'Border' button located in the 'Paragraph' group on the same tab. Here, click on 'Bottom Border' to insert a line directly beneath the text.