1. Install NodeJs

curl -sL https://deb.nodesource.com/setup_7.x | sudo -E bash -
sudo apt-get install nodejs

2. Create a symlink of nodejs to node

ln -s /usr/bin/nodejs /usr/bin/node

3. Install NPM

sudo apt-get install npm

4. Navigate to your App directory

cd /path/to/app

5. Install App's dependencies

sudo npm install

6. Install PM2

sudo npm install pm2 -g

7. Setup PM2 to start on ubuntu boot

pm2 startup ubuntu #This will print a command like below. Run the command with su privilege.
sudo env PATH=$PATH:/usr/bin /usr/local/lib/node_modules/pm2/bin/pm2 startup ubuntu -u ubuntu --hp /home/ubuntu

8. Start Application using PM2

pm2 start app.js

9. Check Application status

pm2 show app

10. Check Application logs

pm2 logs app

11. Setup Nginx as reverse proxy

server {
        listen 80;
        listen [::]:80;
        server_name yourdomain.com;
        location / {
            proxy_pass http://127.0.0.1:8888;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_cache_bypass $http_upgrade;
        }
}

12. Reboot Nginx

sudo service nginx restart