I don't know if your machine is left homing or not, but in your pic the machine is set for zigzag, not straight stitching, so the needle will not come down in it's natural straight stitch position anyway. The zipper foot should have a screw on the back of it to adjust the position of the foot, but you need the machine to be set for straight stitch to use this foot. What you need is a zigzag, or all purpose foot. Left homing or center homing won't matter for this foot. If your machine is low shank, you want this foot:
http://shop.sew-classic.com/Low-Shan...t-SCF55614.htm
If your machine is high shank, you want this foot:
http://shop.sew-classic.com/High-Sha...ot-SCF5555.htm
You can figure out whether your machine is high or low shank on the website. It's easy.
Cari