How to configure on my website

Good day to whom may it concern:

I am new on this but a quick learner too. I would like to add this feature to my website (www.convergere.com). The contact form is very simple and is the one integrated with the theme (zerif lite).
I see some programming to be added, but I wonder if you can provide more information as to what code and where in the website I will need to include this code in order to have this feature and protect the contact form I have.
In advance, thank you for your help.