Please make sure you have read and installed the prerequisites from the module documentation page
The verification page for UnrealIRCd Google reCAPTCHA Module
A rough guide to install which assumes you want to install into /var/www/html/verify (https://example.com/verify) and your webserver user is www-data on Ubuntu/Debian:
cd /var/www/html/
sudo -u www-data git clone https://github.com/ValwareIRC/unrealircd-google-recaptcha verify
cd verify
sudo -u www-data composer install
Just modify the config.php file to suit your needs, nothing complicated!