You need to enter the patient (adult or child) data for which you will be saving an appointment. This happens in the "Family" section, in the profile of your relative or your profile if you are recording a review for yourself.
You select the Profile / Family section, which takes you to the Family section.
There you can use the "Add relatives" button to add information about your minor children. It is important that you fill in all the required patient information - three names, date of birth, PIN, gender, kinship with you so that you can save an appointment.