Amazon Linux v 2.0 does support systemd and comes installed by default:

cat /etc/os-release
NAME="Amazon Linux"
VERSION="2.0 (2017.12)"
ID="amzn"
ID_LIKE="centos rhel fedora"
VERSION_ID="2.0"
PRETTY_NAME="Amazon Linux 2.0 (2017.12) LTS Release Candidate"
ANSI_COLOR="0;33"
CPE_NAME="cpe:2.3:o:amazon:amazon_linux:2.0"
HOME_URL="https://amazonlinux.com/"

rpm -qa | grep -i systemd
systemd-libs-219-42.amzn2.4.x86_64
systemd-219-42.amzn2.4.x86_64
systemd-sysv-219-42.amzn2.4.x86_64`

I need to make my application keep on run, so that i need systemd has to be installed on my linux machine

As others have noted, systemd is not available for your version of Amazon Linux. Fortunately, there are other tools than systemd that solve your problem; I suggest looking at cron. You might take a look at this answer for how to set a program or script to run on reboot on an Amazon Linux box. Alternatively, there's always the cron man page, which sould also be on your machine.

1. First check what Amazon linux version you have runnng on using the command cat /etc/os-release
   2. If it is Amazon Linux Version 2, then it does support systemd and comes installed by default.
   3. If it is Amazon linux version 1, then it doesn't support cause Amazon Linux is ultimately based on an old version of CentOS/RHEL.

if it is version 1 (amazon linux), you just need to switch to any other linux distribution that supports systemd. You can't yum install systemd like a package

It appears the version of Amazon Linux you are using does not have systemd. I'm not sure that any version of Amazon Linux as of today uses systemd. Considering that systemd is a core part of an operating system, it's not something you can just install as a package and expect to work.

If you can't find the packages you need built for Amazon Linux, my recommendation is to start over with an AMI from a different OS. For example, there are AMIs for CentOS that you could start with instead.

I recommend switching to a new Linux distribution. On a more popular Linux distribution like CentOS or Ubuntu, you are far less likely to run into problems with missing packages as you are currently experiencing with Amazon Linux.