How can I remove a retweet from a user who has blocked me via the Twitter API?

I'm using the POST method on the following API call:

https://api.twitter.com/1.1/statuses/unretweet/:id.json

I've set Authorization Type to OAuth 1.0 and "Add params to header".

How can I get my Consumer Key, Consumer Secret, Token and Token Secret for my user account?

I added my phone number and tried creating an App at https://apps.twitter.com/app/, using those keys to send the request.

But I still get this error when sending the request:

{
    "errors": [
        {
            "code": 32,
            "message": "Could not authenticate you."
        }
    ]
}

What am I doing wrong?