From the FAQ:
In order to display an interactive board within a forum post you will need to enter the following code when writing your post:
[pgn ]Your PGN Here[/pgn ] {leave out the space which appears here in each set of brackets, to make it work}
As an example, to view the Immortal Game, you would post this :
Use "reply and quote" from this post, to see exactly what was done, and replace the PGN with your own. You will get the pink error message if the material between the two bracket sets is not a valid PGN.