Custom Fields Via API

Custom Fields Via API

Hello,

How can i fill custom fields via API? I've created a field that appears on my form on "Your informations" and after that it appears on the aditional information, see the image bellow:
Via API i only find documentation to fill the personal data Name, Email and Phone Number.
How can i use this fields?

Also, is it possible to also fill the notes field via API? 


Thanks