If everything went fine, then you may find a folder named nginx in /usr/local path, and if ls /usr/local/nginx/ you can find folders like, conf, html, sbin and may be a logs folder too.
If that's the case, then to start Nginx, simply issue the command:
sudo /usr/local/nginx/sbin/nginx
However, to stop Nginx, use the following command:
sudo /usr/local/nginx/sbin/nginx -s stop
At any stage, you can verify whether Nginx is running or not by using the following command:
netstat -lnp | grep nginx