Click on the Selection button in the left panel, and then select the text that you want to highlight.
Once you complete the text selection, a function selection panels opens above the cursor, in which you can select to Highlight Selection.
Click on the Highlight button.
Draw the highlighted area that you desire.
NOTE: You can change the highlight color by clicking on the color square at the bottom of the left panel.
NOTE: You can enter a comment associated with the highlighted area. To do so, click on the associated comments box on the right and enter the text.