Ice should be applied within the first 5-10 minutes after getting the injury and leave the ice for 20-30 minutes. This can be repeated every 2-3 hours or so for the next 24-48 hours.
If you consider the first 48 hours, and this timings, the frequency should be between 16 to 24 times. If you consider 24 hours, it should be between 8 and 12 times.