1. use reply...not fast reply at the bottom of a page
2. use ie
3. watch your image file size
4. don't forget to click "upload" button

let me know if you have other questions...

if the upload is successful
in the textbox you are replying
there should be such tags

[Upload] file_url [/Upload]

if nothing appears, then your image size is too large
you need to resize your image...
and you have to be using IE while doing this

like this

[...upload=jpg]UploadFile/200481310333721374.jpg[/upload...]

the ... is added by me ... for you to see the details of the tag

if you can see your files using user file management
you can even copy the file name
and type in the [upload] tags yourself
it works too