Follow the official installation instructions.
Python is required on the target host by Ansible so you have to install that.
pacman -S python
Check if ansible can reach the pi:
ansible all -i 192.168.1.256, -m ping --ask-pass -u alarm
Run the playbook.
ansible-playbook playbook.yml -i 192.168.1.256, --ask-pass -u alarm --ask-become-pass --become-method=su
The default user is alarm the password is alarm and the become password is
root.
After the successful run of the playbook copy the ssh public key.
ssh-copy-id -i ~/.ssh/id_rsa.pub raspberry.local
Then finalize playbook will delete the alarm user and disable password authentication for SSH.
ansible-playbook finalize.yml -i raspberry.local, --ask-become-pass