ext_typoscript_constants.txt

# cat=powermailrecaptcha//0010; type=text; label= Google Recaptcha Sitekey: Go to developers.google.com/recaptcha/ and register your domain. After that you can add your site key here.
plugin.tx_powermailrecaptcha.sitekey = abcdef

# cat=powermailrecaptcha//0020; type=text; label= Google Recaptcha Secretkey: Go to developers.google.com/recaptcha/ and register your domain. After that you can add your secret key here.
plugin.tx_powermailrecaptcha.secretkey = abcdef