This is what I usually do:
Bring up another session with the smilie.
Right click your mouse on the address and select 'copy'
Return to the thread here.
Click 'Post a reply'
Type whatever you want in message or just leave it blank.
In the row just above the message box, click the button 'IMG'.
A small box will appear on the top.
Move your cursor there and right click your mouse and select 'paste'.
You will see something like [IMG] http:\...... [\IMG] on your message box. Now everything is ready, you can add more to your message or you just post it.