No, all you need to do is enable the Snaptcha extension. The hidden field will automatically be added to your form and the validation done when the form is submitted. The exceptions to this are member registration forms and the native email module.
To see Snaptcha working on your site, navigate to one of your forms, open your browser’s inspector or use Firebug and delete the input field that Snaptcha inserted. It will usually be towards the bottom of your form’s markup and will have an id that begins with the prefix in your extension settings (“snap” by default). After deleting the input field, submit the form and the error message from your extension settings should appear.
When building your form with DevDemon Forms, ensure that you have enabled Snaptcha support under Form Settings > Security.
While Snaptcha does work with Modernizr, issues have been reported when a website uses Modernizr combined with some front-end frameworks. Setting Snaptcha’s security level to “low” should resolve this issue, however please report this to us so we can investigate further.