The following steps will help you setup your talktalk.net email address on your Kindle Fire HD/HDX. If you're not sure what your email or password is, you can find them in My Account.
Swipe down from the top of the screen
Tap My Account.
Tap Manage Email, Contacts, Calendars
Tap Other Provider.
Enter your name
Enter your TalkTalk email address
Enter your password for your TalkTalk email account. If you don't remember your password you can check and manage your email addresses in MyAccount.
Enter your Account Description as TalkTalk.
Tick the box to send email from this account by default.
Tap Save below your TalkTalk account, and your email is now set up. If you have any problems, head over to the Kindle support site.