Move the cursor to where you want to create a section and click on "Add section here."
Choose Text from the category list on the left, then select the text section you want to add from the menu on the left.
Hover over the section you just added to bring up the "Layout" and "Customize section" settings on the left side of the section.
Click on the text box to change/edit the text.
The text formatting tool will appear above the text you are editing.
Click out of the text box when you're done to automatically save it. If you forget to click out of the box before publishing or making other changes, it will not be saved.