How to save an email as a template
Select the email message you want as a template
Click file, then save as template, and set a name for the template
Set a tag to categorize templates if desired
Select the file location you want your templates saved, and press save.
How to use your created template
Now that the template is created, select file, new, email from template
Select your desired template from the location it is saved in and press "Open"
Add content and recipients to the email, and then send