You can save any email that you have created as a template to be used as a starting point on another email. Simply locate your email and navigate to Step 6 Edit Content. At the bottom right of the page click Save As Template. Give the template a descriptive name. Now when you are ready to create another email, you can choose this template from the My Templates section on Step 5 Select Template.
If this does not answer your question, click here for more information regarding reusing an email.