Advice needed for 15 days old kittens

I must declare that this is the first time I am handling cats, let alone such young kittens.

I have a litter of 4 kittens, and they recently opened their eyes. However now after 5-6 days, all of them except one has one eye closed, with some swelling and yellowish deposits. I fear they have conjunctivitis, and now want some tips on how to treat this condition and what precautions to take.