how do i log out my icloud if i forgot the password

You will have to reset the password, or recover the account. Until you’ve regained access to that account, you cannot sign it out. Obviously, if there was a way to sign out someone’s account without the password, there’d be no point to requiring passwords in the first place.

Start with -> If you forgot your Apple ID password - Apple Support. And if that doesn’t work go to account recovery -> How to use account recovery when you can’t reset your Apple ID password - Apple Support