You can create a simple CGPath like this
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, 0, 0);
CGPathAddLineToPoint(path, NULL, 100, 0);
CGPathAddLineToPoint(path, NULL, 100, 100);
Depending on what you want to achieve you can add different elements to your path like arcs, curves, rects... You can find more about it here.