[TYPO3-mvc] Howto add files to FAL in 6.1

[Joerg Schoppet]

Hi list,

thanks to google I found some information on how to access existing files in FAL through my extbase-extension. But what I'm missing is the part on how to add files to FAL.

Usecase:

I have an order-object in extbase and as soon as an user submits the order I also create a pdf-document of the order. This pdf-document is saved within a configurable folder "normally" fileadmin.

How can I add this generated document to FAL? 

Thanks a lot

Joerg