As per Admin guide:
settingsForm
To use a form for plugin configuration, you can build a form using the form builder then copy and paste that form into the manifest file, or you can build the form directly into the manifest.
Values entered into a form can be accessed using the FormData.values. FormService has functions to assist with validating required fields and displaying errors. Additional validations are built into the HTML and AngularJS code based on the form design, which means Angular will set a field to undefined if it is not valid. These validations can be used to prevent a form from being submitted and show error messages if necessary
how can we use FormData.values?
how to use FormService and where to write this code?