Put your cursor over the first letter of a paragraph in the fourth column, which is the right-most column. When the cursor changes to a hand and/or the color of the letter changes to orange, click.
In the pop-up window, you can then choose a Topic and a Sub-Topic for the bookmark.
The bookmark can refer to one paragraph, a series of paragraphs, or an section.
To make a bookmark that refers to only one paragraph, just click "Make a Bookmark".
To make a bookmark that contains several paragraphs, choose the first paragraph, then click "Include the following paragraph." This may be repeated until the passage in the window is as long as desired. Then click, "Make a Bookmark."
To make a bookmark that includes an entire section place the cursor over the first letter of the Heading or Sub-Heading that is shown in orange in the right-most panel. Then in the pop-up window, click "Make a Bookmark." The bookmark wil contain all the paragraphs in the Heading or Sub-Heading choosen.