Your website config file should be placed in /etc/nginx/sites-available and all you have to do is create a symbolic link in /etc/nginx/sites-enabled pointing to the website you want to enable.
like so from the command line interface in Ubuntu :
ln -s /etc/nginx/sites-available/example.com /etc/nginx/sites-enabled/sudo service nginx reload
Disabling :
If you want to disable a website, just delete the associated symbolic link :
rm /etc/nginx/sites-enabled/example.comsudo service nginx reload
