I'm with campnbob on this and put the vapor barrier on the inside of the stud wall. Fix the outside with a coating on the wall and drain tile around the house and use a dehumidifier inside. If you absolutely can't fix the outside, then just run your 6 mil poly moisture barrier up to ground level on the inside and use some construction adhesive to hold it. You may want to spray a sealer on the wall such as duck's back or dry-lok if you have water coming through the wall but it won't stop it. Keep the stud wall up to an inch from the wall to avoid any wicking. If your walls don't have water soaking through but just has that humid musty smell inside, then I probably wouldn't put a plastic moisture barrier up.