The features "Import" and "New from File" refer to completely different areas of the system :-)

The Import feature is used to import lists of email addresses in the desired format (e.g. *csv, *xls, *txt). To do so, choose Recipients ->Import from the left-side navigation menu.
The New from File feature refers to creating a new email message by using an existing HTML file. Select Email -> New, and then locate the button in the top-right section of the page. This allows you to upload directly into the new message editor an HTML message that had been created elsewhere (e.g. in an HTML editor such as Adobe Dreamweaver). Further changes can be made within the editor, if necessary.

NOTE: this method of creating an HTML message is best for managing CSS as more sophisticated HTML editors make it easier to add inline CSS to your document.