Configuring "Add User to Parent Group" Marketplace Widget

Just a really quick and hopefully simple question about the "Add User to a Parent Group When They Join a Child Group" widget.

I don't want all child group users all across the platform to be added to the parents, just in specific groups. I'm assuming this can be done by using the "Select a Group" in the configuration, but do I add the parent or children? And do I need to replicate this for each group I want to set it for or can I add multiple groups?