Ok, i should know how to do this, but i cant find any documentation on how to do it.
OK, ive rendered my layers in Maya, and for some reason, it wont put the .iff files that it renders into the final Layered PSD so how can i insert the other image files into photoshop and sort them into layers.

Much appreciated to whoever can help

I really don't think it matters the file type as long as it's supported by PS. If it is you can open it in PS and simply take your move tool click on the image and drag into the other open window. Also, you can go to file, import and select the file. If it's not a supported file format which is really rare, try rendering the image out as a different file type if it won't effect what you want the image to do. If it does try to find a format that has similar properties that is supported by PS.