Since the version of NginX in Ubuntu Server 14.04.2 is only 1.4.6, we need to tell APT to install the more recent version of nginx directly from the NginX maintainer.
Add the following lines in /etc/apt/sources.lst
deb trusty nginx
deb-src trusty nginx

From your server download the signing key add it to the apt program keyring with the following commands:
cd /etc/apt
apt-key add nginx_signing.key

Install NginX:
apt-get update
apt-get install nginx

Verify its version:
/usr/sbin/nginx -V
nginx version: nginx/1.9.2
You’re off and running