oh did you mean thumbnail? something like this?
I try to give tutorial..
First, open http://imageshack.us/
You'll see a page like this:
click 'browse', then choose directory in your computer where you save your photo
click 'upload now' button
the uploading process will start
after your photo are succesfully uploaded there'll be page said 'upload successful'
find the 'forum thumbnail' URL like this:
copy that URL and paste it here in the reply box, then send your post :)
hope my explanation isn't too complicated