Wash, dry and press fabric.  If you do this before you sew it up, you'll be able to throw your finished zippered purse in the wash without worrying about it.

Cut two 8 1/2 inch x 4 inch pieces of fabric.  Press a 1/4 fold along one long edge of each piece of fabric.  This is where the zipper will be sewn in.

Pin one side of the zipper (right side up) onto the pressed edge of one of the pieces of fabric.