uhh... PureEvil... WTF... Scripting, Modeling, Prefabs?
Look, first, do yourself a favor and take a good look at the manual. I know it is long, but it will save you time, and us time.
Second. Never use the prefabs, you want to go to the segments tab, and select add new segment. If you can't figure out the rest, once again, read the manual.
This is not mean, it is life. If you can't spend an hour to read a manual then you shouldn't be using the software.
"ye oft de adopte early shalt move mountains, and be gods among men"
He who knows everything knows nothing at all.