Your first label

Let's mark our second section, whose title is ``About This Document''. Click at the end of the section title line, and select Insert $\triangleright$Label. A dialog asks you for a label name, and gives you a suggestion. When you click on OK, the label name will be placed in a box next to the section title.

By the way, you could have put the label right anywhere within the section as well; section references will refer to the last section or subsection whose heading comes before the label. However, putting it on the same line as the section title (or, perhaps, on the first line of the section's text) ensures that page references will reference the beginning of the section.

So far you haven't done anything -- the dvi file will look exactly the same, since labels don't show up in the printed document. However, now that you've added a label, you can refer to that label with cross-references. We'll do that next.