Annie, it took me ages to get my head around my Pfaff. Just be a little patient, and as Maliw says, watch videos, thread and re-thread, read your manual.
The one thing which stuck with me when I was failing to get a decent stitch, was that the handle had to be down - it goes across the tension discs on a Pfaff. Also, make sure that your threads are pulled well down into the tension discs. I put my finger firmly at the top, and pull down - it works for me.
Chin up, it is a learning curve.
Jessie