How can I add a token into suscription box?

Hello,

I would like to add CSRF anti-spoofing to my blog's suscripton form. I am able to add the token input on the form, but I don't know where i have to check the token to know if it is an allowed one or not.

I'm trying this way: https://docs.joomla.org/How_to_add_CSRF_anti-spoofing_to_forms

Regards,