If you mean add images to your forum posts.... then:
Just under the text field you type your message in, there is a section called "File to attach" with a blank area to type next to it, and a "Browse" button to the right. Click the browse button and navigate to the image, and click "open".
When you click on "reply to thread" after you finish your post, your image will be uploaded and shown in-line in the post, at the very bottom. You can add multiple images as well.
If you wanted to add images then more text, then more images, etc, you need to use the forum bbcode "insert image" button (looks like a tree on its icon).