one of the free image hosting sites like Imagecoast or Photobucket.  (Imagecoast is better as Photobucket has given some gals a hard time about saucy photos.)

Once you do that, the photo will have a URL.  Copy and paste that URL in the little window for photo URLs when you begin a post, and the picture will appear when anyone opens your post.

That's all there is to it.

You asked how do you get the picture url.
To get the url, you open the picture and go up to the address bar, and copy the url, or right click on the picture, go to properties, and highlight then copy the url, then you can paste the url in the picture url box on your post. You have to erase the extra "http"in the beginning, otherwise there will be a double "http" and it won't work. Also the picture url has to end in jpg, bmp, or gif.

Not sure if that's what you were asking but that's how I took your question.  

 
Here is a complete "how to"

-- Modified on 7/8/2014 3:17:23 PM