Since we can;t upload images directly to the server, you need to have them hosted somewhere that permits direct linking. I use a free service called
Image Shack, and it seems to work well. There are others out there, but I've never used any of them. Once you get the images hosted, you need to enclose the link to the image in a pair of tags, so if your image is at "randomlocation", you'll want to use [img]randomlocaltion[/img]. If you use Image Shack, once you upload the image, they will give you the image's URL already wrapped in a tag pair usable on this board and many others.