Performing the following calls, you can add or remove users to a specific community:

method: POST

URL: /management/communities/[COMMUNITY_ID]/add_user/[USER_ID].json

method: POST

URL: /management/communities/[COMMUNITY_ID]/remove_user/[USER_ID].json

RETURN: 
{
 "status": true/false
}

With the next request, you can get all info about a specific community:

method: GET

URL: /communities/[COMMUNITY_ID].json

RETURN:
{
  "page": "community",
  "media": {
       "id": "ID",
       "name": "NAME",
       "description": "DESCRIPTION",
       "private_destinator_ids": [],
       "allow_html_posts": true/false,
       "only_admin_comments": true/false,
       "allow_private_comments": true/false,
       "mail_posts": true/false,
       "thumb_url": "THUMB URL",
       "members_text": "MEMBERS TEXT",
       "views": NUMBER,
       "impressions": NUMBER,
       "last_view_time": NUMBER,
       "new_posts": NUMBER,
       "type": "community",
       "collection": "communities"
   },
  "comments": [
      {
            "COMMENTS INFO"
      }
  ]
  "pagination": {
      "current": NUMBER,
      "last": true/FALSE
  }
}