Not sure about it says increase or decrease pressure

There should be a control on top of your machine that is directly over the needle OR, if you have a "door" on the left side of your machine that exposes some of the workings, then there might be a dial inside there. The pressure refers to the amount of pressure the sewing machine foot applies to the fabric. For thick fabrics, you will want to lighten that pressure. For thinner fabrics, you might want to increase that pressure. Use those controls to set the foot pressure. Try it out with a scrap to see if the pressure is to your liking. Good luck!