Installing , Configuring Ansible in EC2 instances:

Installing the Ansible in Master(EC2 instance):

sudo yum install ansible

Configuring the node(another EC2 instance):

In Master generate ssh keypair using:
ssh-keygen -t rsa
copy the public key of Master to ~/.ssh/authorized_keys file in node
cat ~/.ssh/id_rsa.pub (copy the output)
In node open the file in ~/.ssh/authorized_keys and paste the public key of Master :
vi authorized_keys

After completing the above process we can directly ssh to the node(EC2 instance)

Configuring the hosts file in Master(EC2 instance):

In Master go to /etc/ansible/hosts
vi /etc/ansible/hosts
add the group name with in "[ ]" (square brackets) and add the details of the node in the next line (username@ip)

Running ansible commands from Master(EC2 instance):

After completing the above configuration process, run a command from Master to node
ansible -i hosts nodes -a "cat /etc/passwd"

Running ansible playbook from Master(EC2 instance):

ansible-playbook -v createafile.yml