Add a contact form in a header of the website

Hello,
I would like to add a contact form to a website like this website did https://skinandweight.com/body-sculpting/smartlipo-body-sculpting.html but I am not quite sure how to do it. It looks like they used the contact form 7. I see how it is done in the source code, just not sure if they had to add something in the header.php.

Any ideas?

thanks
Diane