Adding text labels and arrows

To label your diagram, there are 2 options:

Label Diagram Tool (recommended)	Label Item
Has an option for an arrow to be attached Supports multiple lines Supports additional text, e.g. text alignment Supports ChemText	Usually used to represent an actual physical label Can be rotated No arrow Supports ChemText

Using the Label Diagram Tool

To add text and arrows to your diagram

First, Select the "Label diagram" tool.

In the property panel on the right, you can edit the text as well as add adjust various properties:

To move the label, select the "Select & Move items" tool and drag the label or the arrow.
To change where the arrow is pointing, click and drag the yellow diamond shapes.
To hide the arrow head, toggle "Show arrow head"
To hide the arrow completely, toggle "Show arrow"
See this article on how to write chemical formulas, subscripts, units etc.