The easiest way to do this without "coding" is to create the new "referred" Lead in Marketo, then sync it to SFDC. Submit the form to Marketo as seen above. The referred Lead's data is stored in the custom Fields. Now you have to use a Webhook in a creative way: use it to submit a Form on your own Marketo instance to create the new Lead. To do so, you need to pass in the "referred" email address in the normal Marketo email field, that will cause a new Lead to be created.
Also make sure that you add a field that indicates the source of this Lead. You need to trigger a Smart Campaign that then syncs this new Lead to SFDC. If you want, you can also push in an SFDC Campaign ID or other information that you want to push to SFDC for this new Lead.
Thanks Jep! I have it all working except one more thing I am trying to figure out. In the webhook I am trying to set the Referral's lead owner the same as the Referrer's lead owner. Is there anyway to accomplish this? I have been trying multiple ways to get this to work but it hasn't been working.
your URL has a typo, it should be localhost with an 'o' instead of an 'a'. It should just work and - by definition- it points to the Marketo instance itself. I do want to mention that our support team considers this a "non supported use of Marketo", so you may not get support from them in implementing this method.
I would use this method instead: How to Use Marketo Forms to Register Multiple Event Attendees The server-side form post method isn't supported and is extremely error-prone.