I figured that quite a few people might have issues with this so this is how to do it.
For links you click on the button that has a picture of a chain with three links. In the top section your put the URL and on the bottom section you put what you want the link to say.
For images you need to use a the IMG url code. It looks like this -->
That should put pictures up in your post.
For linked images you put the link, then in the section where the text goes you put the image code in there.
Hope that helps, any questions feel free to ask!