Taking in the waist of jeans is a common alteration that can be done to make jeans fit better. It involves removing excess fabric from the sides of the waistband and then sewing the waistband back together. This can be a relatively simple alteration to do at home with a sewing machine, and it can make a big difference in the fit of your jeans.
There are a few different ways to take in the waist of jeans, but the most common method is to remove the waistband from the jeans, take in the excess fabric from the sides of the waistband, and then sew the waistband back on. This method is relatively easy to do and it will give you a professional-looking finish.