Good luck, Janie! I think the advice given above, especially the video links and John's assessment are spot on. I agree completely with the idea that either the threads are stripped or the washer is missing. I have faith that if you replace the aforementioned assembly where it attaches to the sink, all will be well.

You may do well to find a book called, "How Things Work in Your Home and What to Do When They Don't". Also, you might want to check


http://www.angieslist.com/

for referrals to qualified plumbers in your area.

Wish I could just drive down and give you a hand. I installed one of these just last week!