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

The yum_repository module can be used to add or remove a .repo file from the /etc/yum.repos.d directory on a managed node.

AVOID TROUBLE

The /etc/yum.repos.d directory should be owned by root, thus you'll want to use the remote_user: root or become parameters.

In this example, the /etc/yum.repos.d/epel.repo will be added on the managed node.

---
- hosts: all
  tasks:
  - name: add the /etc/yum.repos.d/epel.repo
    yum_repository:
      name: epel
      description: EPEL repo
      baseurl: https://download.fedoraproject.org/pub/epel/$releasever/$basearch/
...

In this example, the /etc/yum.repos.d/epel.repo file on the managed node should contain something like this.

[epel]
baseurl = https://download.fedoraproject.org/pub/epel/$releasever/$basearch/
name = EPEL repo

Here is a more complete example.

---
- hosts: all
  tasks:
  - name: add the /etc/yum.repos.d/epel.repo
    yum_repository:
      name: epel
      description: EPEL repo
      baseurl: https://download.fedoraproject.org/pub/epel/$releasever/$basearch/
      enabled: true
      gpgcheck: true
      gpgkey: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
...

And here is how you would go about removing a .repo file.

---
- hosts: all
  tasks:
  - name: remove /etc/yum.repos.d/epel.repo
    yum_repository:
      name: epel
      state: absent

  - name: clean dnf metadata
    command: dnf clean metadata
    args:
      warn: no
...