No you need to sew it to the back piece in between the receipt pocket and card holder part. Just secure with a straight line down the middle.
Now to insert the zip, tuck into one side and sew near to the edge. Now the tricky part, you need to put the other side of the zip into the other end, I ended up sewing the middle bit, then the ends. I think I ended up using all my fingers so hold it in place, as well as pins.