That's quite a broad question, before asking here you should have give a try searching on SO.
Anyways, I'll tell you broadly how can you do it.
First of all go through the official documentation of Graph API: Graph API Reference.
You'll find each and every API which can be used to fetch the data. For example: /group
, /page
. You'll get to know what kind of access token with what permissions are required for an API call.
Here are some API calls useful to you-
to fetch the group/page's posts-
/{group-id/page-id}/posts
to fetch the comments of a post-
{post-id}/comments
to fetch the group/page's photos-
/{group-id/page-id}/photos
and so on. Once you'll go through the documentation and test some API calls, the things would be much clear. It's quite easy!
Hope it helps. Good luck!