502 error during Wordpress installation on nginx

Hi all,

I am getting a 502 error when trying to access the Wordpress installer (index.php).

My error log says (replaced my domain name with mydomain.com):

2018/12/17 21:04:30 [crit] 5239#5239: *29 connect() to unix:/var/run/php-fpm/php7.2-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 123.162.124.123, server: mydomain.com, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php-fpm/php7.2-fpm.sock:", host: "mydomain.com", referrer: "http://mydomain.com" 

when I check my server this file does not exist, I have php-fpm but no .sock file

 $locate php-fpm
/etc/php/7.2/fpm/php-fpm.conf    
/usr/sbin/php-fpm7.2
/usr/share/doc/php-fpm
/usr/share/doc/php-fpm/changelog.gz
/usr/share/doc/php-fpm/copyright
/usr/share/man/man8/php-fpm7.2.8.gz
/var/lib/dpkg/info/php-fpm.list
/var/lib/dpkg/info/php-fpm.md5sums

my question:

1. How do I resolve this 502 error?
2. What is the socket file (and do I create it myself or should it be automatically generated?

Many thanks