I'm trying to add a custom field to my community's lightning-based self-registration form.

I've created a Contact field set and named it: SelfRegistration
The contact field I'd like to add is a custom field called: Company_Name

In the community builder there seems to be a place where I can indicate the API name for this field set to add it to the registration form, but I'm unable to figure out the proper syntax/format. Any guidance would be greatly appreciated.



Things to note:
If its easier to add it onto the User record instead of the Contact record that should be find four our use case.
Eventually we would like to add a Job Title text field as well.