Hi!
• Usually the paths is
/etc/nginx/sites-available/
• It should have a .conf file with your domain name yourdomainname.conf
in my case it is "stickit.gr.conf"
• Replace the contents of the yourdomainname.conf , with the above code ( keep a copy of the original file)
edit the " [REQUIRED EDIT] the name of your admin directory" parts
• Save the file , restart nginx ( you can use "nginx -t " to test if the conf file is ok )