You probably want to save your changes, after you have changed a template in the designer.
All export/import options of templates (apart from a simple save) is covered in the Library here.
To save a template you click the save option on the upper right corner:
This enables you to save a description of the changes together with the template in the template revision log. The save is not a full revision, but only your description of the changes.
The pop-up window for the revision looks like this:
The save is also covered here. The revision log can also be displayed in the designer.
From the left to the right, they are:
Open a template
Upload a template
Download a template
Convert to email
Click this icon:
If you want to open an existing template.
You can upload an .ift template directly to the designer with this icon:
Then you are prompted for the .ift file to upload.
If you want to convert a normal template into an email template, then you can click this icon in the top right in the designer:
If you click this icon the template is now considered an email template and the template name is Untitled template and you need to save the template as a new email template with the extension .ifm.
You can download the changed template as an .ift file to your local PC, if you select this option.