Jim, just follow this:

1. Make sure you enabled “contact form 7″ in Math Captcha settings.
2. Go to the CF7 form where you want to make use of Math Captcha
3. Find a dropdown with form fields, select Math Captcha and insert it into your form.
4. Log out or set “Hide for logged in users” to “No” to see the changes in your form (by default if you’re logged in you will not see the captcha)