Keys are encrypted using ansible-vault.
Get the latest .vault_pass.txt from a team member and run chmod 600 .vault_pass.txt to help ensure it remains a secret.
Then in your shell config add
export ANSIBLE_VAULT_PASSWORD_FILE=.vault_pass.txt
Next set up your hosts file by copying hosts.example to hosts and optionally adding your sudo password for safecast's infrastructure to the new file.
Once this is all set you should be able to run a dev deployment with:
> ansible-playbook playbooks/dev.yml