I put a zipper in using a 12" zipper. I cut 4 rectangles 10.5" x 2". sew right side in -on three sides. (short sides and one long side.) Turn and press. I sewed this in at the time I was putting in the handles and sewing in the lining. I put these plackets between the handles and lining. I centered them with the handles(one on each side.) I sewed the zipper onto these plackets after all sewing on the bag was done. I started the opening of the zipper at one end of the placket and let the closed end of the zipper extend beyond the placket. this gives you a wider opening when opening a your bag. I put a small square tab at the end of the zipper. (found on most purses with zippers.) I added a ribbon to match my material in the zipper head. When looking for zippers, I found there is a lot to chose from but the color I needed was only in a nylon dress zipper. I did not take any pictures but it was really easy to do.
If you need more directions or want me to draw pictures let me know. Phannie