How to trigger automation with new contact using the members/signup route?

I am trying to trigger an automation workflow through the members/signup route with a new contact. My current attempt is not working, I'm adding the new contact to a group when I hit the members/signup route (this is currently working). My automation workflow audience is set up to be this particular group, with the trigger being the signup of the form whose ID I'm using when posting to the members/signup route.

Do I need to add the new contact to the group before I POST to members/signup?

What is the recommended way to trigger automation for a new contact through the Emma API?

Thanks for any help!