[TYPO3-english] How to allow attachments in TMailform

[rsbrux]

Our website uses TMailform (pil_mailform) to implement a Contact form.  We would like to allow users to add an attachment (e.g. a picture or graphic) to the resulting e-mail.  According to the documentation (http://docs.typo3.org/typo3cms/extensions/pil_mailform/Index.html), this has been supported since version 2.0.0 (current version is 3.0.4).  However, even though this possibility is mentioned in the documented example, I find no information or examples of how this is done, nor do I see any such possibilities in the back-end configuration of the plugin itself or of the corresponding element in the page definition.  How is this done?  Where can I find the corresponding documentation?  TIA!
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Typo3 4.5.18 - 4.5.29
PHP 5.3
mySQL 5.5 x64
Windows 8 x64