The invite email mentions the reward of $7 towards your first delivery in the title. It gives you a few more details, and a "Redeem your credits" button.
Updated sign up flow
In previous recordings, to sign up on this page you'd click a button that would open an overlay where you'd sign up with your email.
This time, there's a "Continue with Facebook" option, or you can sign up with your email on the page without having to open an overlay. The sign up form has also been updated very slightly. For example, the password field now has a "show" option and the text in button to submit the form has been updated.
Signup to get credits
Clicking on the "Redeem your credits" button in the email takes you to a web page on doordash.com asking you to sign up to get your credits. You can sign up with Facebook or with your email
Once you're registered and your phone number has been validated, you get a success message.
You're redirected back to Doordash from this page automatically.