Have you read this thread at all? There is a link to the relevant wiki article in post #2.

More importantly, please see the step by step instructions provided by michaaa62 in this thread - on the same page. Y'know, like right above your post.

Alternatively, if you already read that and still don't get it, I'd recommend not attempting this procedure. It's quite possible to screw up your N900 if you get it wrong, and you'd need more skill to fix it than you would to break it. You should ask yourself why you want to attempt this and whether you really need the result.

If you ask specific questions, chances are someone can help you, but please don't ignore the effort already provided by other people in this thread.

Finally (and this applies to everyone, especially bbkshine, who posted the original question)...

If you found the information posted by michaaa62 to be useful, please click the Thanks! link at the bottom right of that post. It will be appreciated by michaaa62 and just as importantly lets other users quickly see that that post was appreciated by several people and is therefore probably useful for them too.