POST request to /agreements/{agreementId}/formFields

Hello,

I have a question regarding this endpoint and just not sure where to look.

Once you uploaded a file using the /transientDocuments endpoint and then created an agreement in AUTHORING state using the /agreements endpoint, how does one add specific form fields to that document? I see it says something about using a Template ID, but not understanding what that is for or how to get the Template ID.

Thanks all, and appreciate the patience with me.