I need help!!

Ok so i'm going to be writing a story soon but i need some help with the layout! You know how when you read a story the someone wrote and there are pics in the background??? I hope you guys are understanding what i am trying to say lol cause i am very confusing at times! but yea anyways and It say you have to have a url but what is that? Can you just get a pic from google and put it in there? I don't get it! So if you can help that would be great! So yea plz help!