To start editing, adding, and configuring your templates, you'll need to go to the Templates page. You can get there by clicking on your profile on the top nav bar, and selecting the "Templates" item.
This will take you to the templates admin page. From this page, you can see all your organization's templates, both live and in draft mode. You can edit these by clicking into each one, or create new ones by clicking the "+New Template" button.
Good luck and let us know if you have any questions about how to get started with this feature!