1. Go to ImageShack
Click Browse and find your doll.
2. Upload your doll
If you want to upload multiple dolls at once, you can click browse again and add them. Otherwise, click Upload Now.
3. Get the code
You will be given a number of codes. Select the one that says Forum Code and copy it.
(Alternatively, if you have an ImageShack account, you can copy the Direct Link and add image tags when posting.)
Now all that's left to do is to paste the code you got into a forum post.