Chloe:
There’s a Facebook group of machine knitters. There are lots of videos on YouTube. I looked up your machine and it is a standard gauge. Three plies doesn’t tell us the thickness of the yarn. My standard gauge will handle DK or sport weight yarn, but no thicker. In addition to the stitch dial on the carriage, there may be one on the yarn mast which regulates how easily the yarn passes through the dials on the mast.
Beth