Adding an Apple Watch to my account for a child

I'm finding your post after searching for a similar problem. If you set up an iCloud account and create a family set up you can pair the watch to your phone and set up for a family member to use. This allows many choices that can monitor your child's use and add whatever parental control you feel comfortable with. In order to make the pairing work an iCloud email account/password that you set up earlier will be needed for completing the setup. Skip the cellular set up on watch until calling 611 or in person to add a line to your plan. When the number is added you can complete the cellular set up on the watch and also access the watch settings on your phone through the Apple Watch app. I'm attempting to switch a line from a Timex family connect to a series 4 Apple Watch. I'm not an expert but I'm hoping this helps you. I'll add to the post if anything else comes up. ¡Buena suerte!