From the help portion of the site:
Can I upload an image or attachment to my post?
You may attach a file to your post. The allowed file format and the maximum file size will be displayed when you click on "Click here to upload".
For graphical files (jpeg, gif, bmp, png), you can embed the uploaded picture in the post directly by checking the box: “Embed picture in post”.
The size must be no larger than 100KB, so you most likely will have to resize(by way of editing sw, ms paint) and save that edited file to your harddrive. Once you click upload, click "Browse" this will allow you to locate the file on your harddrive that you wish to post. Once you have located the file click on it and click "Open", it will then download and say if successful once completed. Once this is done click "Ok" and check the "embed picture in post" box.
The other option is a hosting sight then post the link for members to view your pictures.
Best of luck, hope it helps.