Your password is case sensitive, so double check your caps lock! If it was on when you made your password, you'll need it on when you enter it.
Your keyboard setting must be US. You can usually change it by looking at your start bar on the bottom, there will be a keyboard icon.
are you using your in-game username or your forum one? You NEED to use the in-game one
Also are you getting any error messages and what do they say?