This depends on what you are using easiCaptcha with, select from the following links for the easiCaptcha that suites your needs:
If you want to use easiCaptcha in Freeway 4 Pro or above then select this PHP easiCaptcha tutorial, this is an action that can be used with Freeway and avoids hand coding as it is just a matter of adding the actions to your form.
PHP easiCaptcha - easiCaptcha action for use with Freeway 4 + Pro
The following link is to the tutorial page for adding easiCaptcha scripts to your web form.
easiCaptcha scripts - For those that prefer to hand code the easiCaptcha scripts in forms.
If using easiCaptcha with your form you may consider looking at easiForm, this is a script to take care of your form handlimg process, see here.