If your parents exhibit the symptoms such as high temperature and a new dry cough, they/you should call NHS 111 for further advice and information. If you feel it is an emergency, then of course you should contact 999.
If you need to prepare them to go into hospital, you and they need to make a list of their medication, to pack a small bag (pyjamas, toothbrush, glasses etc) and to also make a list of family/friends with contact details. Read more information on getting the best care in hospital.