A couple of things to check on - did you drop the feed dogs? For some that doesn't make a difference, for others is does. Be sure and use the correct foot - a free motion or darning foot. Make small quilt sandwiches and practice. A single hole plate would be a help also.
Find or draw designs on paper or a white board to practice before trying to do it with your machine.
Don't give up! Keep trying, but when you practice, try something different. If you keep trying, but dont' try to change anything, it won't get any better.
I have taught free motion quilting at our guild and many people who thought they couldn't do it, are now on their way to feeling better about it.