Create a Mail Template

Click Add Template in the "Mail Templates" section of the "Manage Tempates" dialog. The "Add Template" dialog for a email template looks like the following:

You have to enter the following information:

Name: Name of the template.
Subject: The subject of the email. Issue variables will be replaced.
Body: The body of the email in text. Issue variables will be replaced.
HTML Body: The body of the email in HTML format. Issue variables will be replaced.

If you click the question mark icon in the top right corner of the template editor dialog, a help page is displayed that lists the replacement syntax for your Jira fields.

When done, click Save.