Putting a zipper on a jacket can be tricky, especially if your jacket has several layers or a lining. Using a sewing machine is typically easier, but you can also sew the zipper by hand using a needle and thread.
Lay the jacket on a large, flat surface.
Use a seam ripper or a small, narrow scissors to remove the threads that hold the old zipper in place. Note how the zipper is secured, so you can repeat it. Sometimes jackets have several layers of fabric or an attached lining. Keep track of how the jacket layers are assembled.
Turn the jacket inside out. Slide the closed zipper into the folds of fabric that held the old zipper. Make sure the zipper pull is facing outward. Use pins or baste the zipper to hold it in place.
Check the zipper to make sure it is straight and aligned correctly.
Use a sewing machine to sew the zipper in place between the first layer of fabric. Make sure the zipper lies flat and does not pucker. Use backstitching to secure the ends. Pull out the pins.
Sew any remaining layers or linings that cover the zipper fabric and finish the jacket.