So the reason I decided to create a own post for this is because this is one of the things I had some trouble finding out what to do, and I can imagine how much easier it would be to create a tutorial instead of writing "Upload it to an image hosting site like photobucket".
There are several different ways to upload the button to a server. I am no computer expert, but the way I understand it by uploading the picture to a server you get an Internet address to your photo
For this tutorial I shall be using Photobucket.
First create a user and log in.
Then you click "Albums" in the tab, and you will see this page:
The URL you see is what you will need to create your button!