In the New Email Module,
Open the Email Template that you are working on:
1. To change the properties of the text
Please go to Appearance > General settings. You will see options to set Font, Line spacing, RTL (Right to left) direction etc.
See Here: https://www.screencast.com/t/pxrk4lKBdh0
2. How to give custom settings to Heading?
In order to change Heading properties, Please select Headings menu to see properties. For Each heading you can set your own custom definitions like font size , colour , bold or italic and line spacing.
3. Merge Tags:
This is basically used to personalise the emails. All the data that you have collected during registration process is what is displayed here and can be chosen.
See here: https://www.screencast.com/t/m0aq4qeide
4. Special/Action Links:
Please see this article here.