Log in to your User Account.
Click "Add/Edit Family Member" button at the top of the dashboard on your user account page.
Click on the Pencil Icon as shown to edit one of your family member's accounts.
Under here, you will be able to edit their account information, just like you would for your account (My Profile).
You will also be able to upload any documents required by your organization. (Ex. a birth certificate or a driver's license)
Be sure to click Save Profile Info to make sure the changes you make are saved.