How can you cure blisters from a sun burn?

Cool the skin. Watch http://www.Youtube.Com/watch?V=xrfaj3wssis to learn a little more.
Don't pop them. Apply cold compresses, take Ibuprofen or acetaminophen, and avoid popping the blisters. Apply a topical antibiotic ointment. If the blisters are severe or rupture, see a dermatologist to treat possible infection.