Well, as the FAQ points out, you need to post that picture to a server on the Web.
If you leave it on your PC, no-one will be able to see it, you have to upload it "somewhere".
That can be, in my instance Sony Imagestation, or you can upload them to this site and they will be added to the zillions of pics. already there.
I haven't done that yet, but I'm guessing you just cut and paste the image ID into your Post, similar to what I did for the remote URL.
Have a play, you won't get shot for trying
Some of us [more mature people] have been playing with a post which was created in error
I don't think anyone would mind you having a fun time there either.
Look for "Oops created a thread... please delete" under the Main Forum.
If it doesn't work you can edit your post until you crack the code