If you are referring to posting an image, you can go here http://imageshack.us/ and create an account (it is free), and then upload the image in ".jpg" format (making sure to select the "remove size/resolution bar from thumbnail?" option).
Once you have successfully uploaded the image, copy the "Direct Link" address to the image (usually the bottom address offered for the uploaded image), and then paste into the "Image" link option here.