The IFrames interface comprises 3 tabbed areas - File, Advanced and Options.
File
Set the most common attributes for the iframe including URL, Alignment and Dimensions. See Creating an editing iframes
The URL for a local file can be selected using the File Browser icon at the end of the URL field.
Advanced
Set advanced attributes for the iframe. See Advanced Options
Options
Set options specific to Youtube, Vimeo and Dailymotion iframes. See IFrame Options