How can I put reCAPTCHA v2 in registration
which version of MyBB exactly you are using ? NoCaptcha reCaptcha method is available since MyBB 1.8.4
admin panel >> Configuration (settings) >> General Configuration >> CAPTCHA Images for Registration & Posting
select NoCaptcha reCaptcha and add both the API keys (Public & Private keys)
MyBB 1.8.5 Thanks :*
And how to do it in the center ?