You can attach the file to the email if you like, or you can add a link to the file in the email.
When you add File Upload to the page, look in the bindings panel. There is a binding group called WA Uploaded Files (Name of File Field). In this binding group is a binding for server file name and server directory.
In the Universal Email behavior, click the paper Clip icon to add an attachment. For the Enter value option, click the lightning bolt icon, from the bindings panel, expand the Uploaded Files binding group, and select the Server Directory, then copy the server directory binding code and select the server file name binding. You will need to past the server directory binding code in front of the server file name binding code.
If you would like to add a link to the file in the email, you will need to use the Server File Name binding in the link path:
<a href="http://yourDomain.com/uploadpath/<server file name binding>">Click here to download</a>