We launched the new version of Bookwhen in mid-2016. If you created an account before then you might still be using the old version, or 'v1'.
Both systems will be kept running at the same time, so there's no need to change, but the new system is where all the new features are.
The two systems are not connected in any way other than an option to import a v1 account into a new version account. This is for existing customers on the v1 system wanting to start using the new version.
Your login details (email and password) on the v1 system won't work on the new system, so you'll have to sign up for a new account if you want to start using the new version.