How to Add a Newsletter Subscription Checkbox to Contact Form 7 (Free)

Do you want to add a newsletter subscription checkbox to your Contact Form 7 forms?
Or perhaps you just want to convert your entire contact form into a newsletter subscription form (without users having to tick a checkbox).
If so, then this guide is for you.
And the best part is, you’ll be able to do all this for free, and without writing any line of code