In order to sign in to your Contour account from either the website or from Storyteller, you will first need to have registered an account.
You can do that by visiting http://contour.com/users/new. If you don't recall your password, you can have a reminder sent to you by visiting http://contour.com/sessions/forgot_password.
In some cases, you may try logging in with your username instead of your email address. That can often correct problems with loggin in to your account.
Signing in to your account is not required for using Storyteller. You only have to sign in (log in) to your account in Storyteller or on the website in order to upload and share your videos.