Help with installing Cabins and Sounds

[Philip]

Hello,
I have been downloading numerous trains from this site and their cabins and sounds that go along with it. But I have no clue how to install these cabins and sounds to the train. I have tried installing the files into the train folder. But when I start up the Train Simulator and I click on the train I want to drive, an error pops up saying that a cerain "SMS" file could not be found and "failed to create a cabin view." If anybody could help me with this problem that would be great, thanks.