Q. How do I add Tags to the content text ?

A. Tags are located at the right of the screen when creating an email or mass email.

These 'tags' are substituted with the named property when the email job runs. For example, using Hi {FIRST_NAME}, would result in text saying 'Hi John', 'Hi Sarah' and so on as appropriate, when the email job executes.

Hover your mouse over any of them for a full description of what the tag is substituted for. To add them to the context just click on the + icon.