How Do I Enable Family Sharing For iTunes Accounts In iOS?
Open the Settings app on your iPhone or iPad and navigate to iCloud > Set Up Family Sharing. You will be taken through a series of steps to setup Family Sharing as the Family Organizer. The Family Organizer agrees to pay for all music, book, and app purchases initiated by other family members.
Continue through the steps, making sure you have a valid payment method on file. You will also be presented with the option to share your location with your family. The final step involves adding family members to your Family Sharing account.