If you are having issues with this trivial of a task I'd recommend Flexi... I'm not trying to be a jerk or elitist in this sense. Flexi simply is one of the best programs to get you started in operating a wideformat printer/plotter, It is just down right simple to operate and functions much like Corel in many senses.
As you gain knowledge and experience you can move to any RIP you are willing to learn. I say this with experience as I was in this position 8 years ago when I was thrust into vehicle wraps for the company I worked for. I already knew photoshop, illustrator, and corel so flexi was just a extension of those programs in a sense and I quickly learned problems, solutions, tricks and methods many of which came from lurking here.