How do you fix a crack in the screen of an iphone?

If you've got your phone covered by either mobile or home contents insurance, then contact your insurer and see if they will help. If not you will need to take it to a repair shop and get it sorted. If its cracked but does not affect your phone working, and you can't get it repaired then best to buy a waterproof cover for the back which will not only help to protect your phone from further damage. A cover will also hide any damage if you buy either a coloured or patterned cover.