Ana I think you just type ICE before the appropriate name in your contact list.
That is what I have done. Thus, John Smith becomes ICE John Smith.
I had to go on a speed awareness course (had done 36 in a 30mph area).
The course was facilitated by a retired policeman. He told us that if there is an accident, they go through the injured person's mobile phone contact list under I for a name beginning with ICE. They would then ring that number. If there were no ICE numbers they would look for other clues, like 'mum", "Home" and go through the list until they found someone.