As simple as like this,
make sure to change example.com to your domain (or IP), and 8080 to your Node.js application port:
server {
listen 80;
server_name example.com;
location / {
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $http_host;
proxy_pass "http://127.0.0.1:8080";
}
}
Source: https://eladnava.com/binding-nodejs-port-80-using-nginx/