Your first line should read
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create("https://api.imgur.com/3/image/8ABRUYt");
The correct url is "https://api.imgur.com/3/image/{id}" - {id} being your picture ID.
Your post helped me greatly getting started on simply viewing a picture from imgur! I would vote you up, but that requires 15 reputation :( I'll be sure to rep you, when I can :)