As far as I know, you have to upload it to a third party site (photobucket, imageshack, deviantart, etc), then take the direct link from said site and place it between the img tags.
I just recently learned how to upload the images from deviantart. Right click on your image in deviantart, then select "View Image Info", then copy the link that is highlighted. That is your direct link from deviant art. The other two I mentioned should have an area on the photo that specifies which is the direct link.
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