Open the lid. On the left-hand side is the window in which you can see what the tension is. The dial is on the side, in line with the window. With your fingers, feel for a vertical wheel, and slide (roll) it up or down to increase or decrease the thread tension. The normal setting is in the white range between 3 and 5. To check the tension, set the machine for zigzag stitch by entering program 10. Sew a short seam. The threads should interlock in the middle of the material.