Permission is denied while connecting to server with ansible via ssh

I’m getting the error below when I’m writing this

ansible -m ping all

host1 | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: Permission denied (publickey,password).\r\n",
    "unreachable": true
}

I have gone through all the steps in this tutorial and now I’m stuck at step 3. https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-ansible-on-ubuntu-16-04

Any help is appreciated.