Encrypt creditionals befor send via API

Hello,
I want to store credentials via API. I found here how can I do that https://docs.cozy.io/en/cozy-stack/bitwarden/#post-bitwardenapicipherscreate. Problem is that in my BitWarden login, password, etc is empty. I know that I need to encryopt data before send but I can't found information how can I do that. Could you help me?
