Open the game in question you want to annotate. Click on the Moves tab, and copy the FEN text.
Then while starting a new topic (or posting in an existing topic), click on the chessboard icon just under your name and above the box you're typing in. Select "Game or Sequence of Moves", and hit continue. Select "Use a FEN string", and paste into the field. Hit continue. Then its a simple matter of scrolling through the moves and entering comments whenever you want.
Ah, I see, thank you .
Check that, FEN I believe may only post a current position. Under the moves tab, you can download the PGN file. Then open it with Notepad, copy the text, and paste it into the PGN field when creating the post. Sorry.
Don't worry , thanks for the help.