Adding pre-mixed 5.1 surround sound

I've never added 5.1 surround sound to FCP and was wondering if anyone knew the process.

The sound designer mixed 5.1 in protools and everything is finished. Now do I just drop the sound file in the timeline and export as is, since he already mixed all the channels and it's already in 5.1 or is there some type of setting I need to set in FCP?

I know if I send it to compressor, I would select dolby surround sound, but I'm just looking for confirmation on what is best to do or if anyone has past experience with this.

Thanks in advanced.