The white things are drive rails. You need to mount those on the cd drives and then slide them in, they should make a click to let you now they're in. Remember the metal tab points toward the front of the case.
Purple things? do you mean the series of squares in a line on the left(http://www.newegg.com/app/Showimage....129-124-12.JPG
)? I think those are just a place to run cables through to organzie things. At least thats what I use them for. I have a case very similar to this one.
You should probably stick a fan near the bottom in the front as an outtake or if you want it as an intake switch one of the rear fans as an outtake.