I am using the contact API for add new contact. So I want to save Origin Source in API but now I am unable to select the drop down value of Origin Source, because it's read only property. And I am not able to change this property. Please find the screen shot.
The Original Source properties reflect the first known source through which the contact found your website. These source properties are automatically set by HubSpot, and this property cannot be changed in the UI or via the API. If you're looking for a customizable property to use to track the creation source, you could create a custom contact property.
A contact created after filling out a form could have any value for Original Source, since those properties track how that contact was first seen on your website. If they discovered your website through a search engine, their Original Source will be Organic Search, regardless of which form they submitted. If you're looking to identify the first/latest form submitted, you can check out the First/Last Conversion properties.