How to share my blog post to facebook page and group using facebook graph api

I have a problem doing a project of my own. How to share my blog post to facebook page and group using facebook graph api.

In the facebook graph api it is written that to post a page use this.

POST https://graph.facebook.com/page-id/feed
  ?message=Hello Fans!
  &access_token=your-access-token

I create a page where I am the admin of the page. My page is now live.

I have added manage_pages and publish_pages permission to my api added added the token.

But when I submit the data in the above url it throws error that is shown below

"error": {
        "message": "(#200) Requires either publish_to_groups permission and app being installed in the group, or manage_pages and publish_pages as an admin with sufficient administrative permission",
        "type": "OAuthException",
        "code": 200,
        "fbtrace_id": "H+YtIYAin/9"
    }

I can’t find out what I am doing wrong. I have google it but did not find a solution. Thank you in advance for helping me