Basics of hand tailoring - tutorial on how to install zippers on clothing.
Zip steps:
Cut the middle point of the zipper and mark it with a water-disposable pen.
Cut the middle point on the opening of the finished small bag (same for other items of clothing).
. . .
For specific DIY methods, please refer to the graphic tutorial below, which has been described in detail in text on the picture. I believe that after this study, you will no longer have to worry about the problem of zippering!