If you are not familiar with modules, check out Ansible - Getting Started with Modules.

docker_login is part of the community.docker collection. Typically, the community.docker collection is not included in the default Ansible collections. The ansible-galaxy collection install command can be used to install the community.docker collection.

ansible-galaxy collection install community.docker

The docker_login module can be used to log into Docker Hub. This is often used when you want to pull and image from a private repository, which can be done using the docker_container module. In this example, the password for Docker Hub is stored in a vault encrypted file

---
- hosts: all
  tasks:
  - name: Log into DockerHub
    docker_login:
      username: john.doe
      password: "{{ docker_password }}"
      registry: your.private.registry.io

  - name: create and start the 'foo' container from the jeremycanfield/my-image:latest image
    docker_container:
      name: foo
      image: jeremycanfield/my-image:latest
      state: started

  - name: Log out of DockerHub
    docker_login:
      state: absent
...