Ogar is an open source implementation of the Agar.io server writen in Node.js and available on GitHub. The full documentation is available there. You can get it up and running pretty quickly if you already have Node.js installed. If not, follow this tutorial or use the Node.js One-Click application available in the control panel.

One Node.js is available, you will also have to install git so that you can grap the source:

sudo apt-get update
sudo apt-get install git
git clone git://github.com/OgarProject/Ogar.git Ogar

Now we can install its dependencies using:

cd Ogar/
npm install

Finally, we can start Ogar with:

node

Now to connect to your private server, visit http://agar.io/?ip=111.111.111.111:443 replacing the highlighted section with the IP address of your Droplet.

This is really just a quick way of getting up and running. If you plan on keeping the server in use for sometime, check out this tutorial for info on how to get your Droplet production ready:

• How To Set Up a Node.js Application for Production on Ubuntu 14.04

and how to make server to 24/7?? pls