ReCAPTCHA box in subscription process

Hi,

Thanks in advance. l am trying to do is the following:

1. User enters their email address into the ‘stay up to date’ box and presses ‘Subscribe’ (ref to image 1)
2. A new window appears which displays a reCAPTCHA box where the user follws the instructions to prevent spambots from adding their emails to my email list. (ref to image 2 to see what l would like to appear)
3. User receives a mailchimp email ‘confirmation/thanks for joining us’ email. (ref to image 3)

I have already achieved step 1 and step 3. I don’t know how to do step 2.

Thanks