How can i use ice to relieve jaw pain?

Not Ice but heat: Jaw joint pain may be related to either true inflammation of the jaw joint or more commonly muscle spasm of the jaw muscles. I would recommend heat (heating pad) and an analgesic such as asa, Ibuprofen or tylenol (acetaminophen). Seeing your dentist or oral surgeon for a definitive diagnosis is paramount.

On outside of face: 20 minutes on and 20 minutes off. See your dentist asap.

Yes but modify: I agree with many of the answers here. An acute injury to the mandible or face should be iced. I often recommend a frozen bag of peas or popcorn kernels so that the cold can adhere with contours of the face and jaw. Ten minutes on, the 10 off is usually adequate. Don't leave the cold on for too long of a period at a time. Moist heat is usually used for injuries and pain that has lingered.

Hot or cold: Sometimes relief better with hot (muscle spasm) sometimes cold (inflammation). Try each. But, you should find out why you have jaw pain. See a board certified oral & maxillfacial surgeon.