Password Reset details should have been set up for the email address so that an alternate email and or mobile number can receive a password reset. Please do try the Forgotten your Password? option. If there's an alternate shown that you recognise from the hints, and have access to, then please reset the password.
If you can sign in to TalkTalk Mail then for routine password changes select the password reset to be sent to the account itself or, preferably, update Reset details via the main menu then use the Forgotten your Password journey.
Provided the password has not been reset then if you're a TalkTalk broadband or MailPlus customer and know the current password you can change your email password in MyAccount > My Services > Manage TalkTalk Mail.