How to send a campaign using a template you created
When you'll create and save a template, you'll be able to choose it as a base for your campaigns.
Whether it's a regular campaign or an automated email, go through the first setup step, and click the "Save & next" button. On the next screen, you can choose the base template for your email. If you have created some templates, you'll see them in the Your designs section.
Click on the template that you want to use, and you'll be able to modify it in the editor.