いったんは、ask-vault-passと、createをおぼえるといいと思いました。
ansible-vault --help Usage: ansible-vault [create|decrypt|edit|encrypt|rekey|view] [--help] [options] vaultfile.yml Options: --ask-vault-pass ask for vault password -h, --help show this help message and exit --new-vault-password-file=NEW_VAULT_PASSWORD_FILE new vault password file for rekey --output=OUTPUT_FILE output file name for encrypt or decrypt; use - for stdout --vault-password-file=VAULT_PASSWORD_FILE vault password file -v, --verbose verbose mode (-vvv for more, -vvvv to enable connection debugging) --version show program's version number and exit