Open cloud shell (top right corner) and execute this commands

sudo -s
cd ~
git clone https://github.com/shodan0x00/gcp-terraform-ansible-pipe.git /opt/bootstrap
bash /opt/bootstrap/install.sh

copy remote_user from /opt/bootstrap/ansible.cfg
copy key file /opt/bootstrap/ssh-key

ssh -i <ssh-key> <remote_user>@<vm-public_ip>

Script generates following files from created VMs and generated keys:

/opt/bootstrap/ansible/ansible.cfg 
/opt/bootstrap/hosts 
/opt/bootstrap/ssh-key

Where 'ansible.cfg' file has ssh username, 'hosts' has public IP associations of created VMs and 'ssh-key' is a private key used to ssh into those VMs.

Copy them into your local machine, go into the folder where ansible.cfg reside and launch with this command:

ansible-playbook -i /opt/bootstrap/hosts /opt/bootstrap/ansible/postgres-kafka-nifi.yaml --private-key /opt/bootstrap/ssh-key