To view or edit an email click on it in the Manage Emails list.
Click 'Manage Emails For This Event' then click the '+ New Custom Template' button.
Enter a 'Template Name' and 'Subject' for your email then add text to the 'Body'. Note that you can add merged fields to the body of the email by clicking the button for the field you wish to add in the 'Merge Fields' list. This will merge the relevant data from the system into the email, e.g. 'event title'.
Thereafter, choose a 'Recipient Group' that matches who you wish to send the custom email to.
Select any 'Additional Settings' and/or add attachments, then click 'Create Email Template'.
Your custom email will now appear in the 'Manage Emails' list in the 'Custom Templates' section and can be sent by clicking 'Send'.
See also Designing Emails