Waves Keeper is an account that works through a browser extension
To create a Waves Keeper account you'll first have to download the Waves Keeper browser extension here.
Once you've installed and opened the extension, this window should pop up, hit 'Get Started'
Now you'll be able to create a password for your account.
After you've created your password, select 'Create a new account'
Choose an avatar and hit the 'Continue' button.
After this, create your Account name and it is recommended to create a backup before hitting continue.
The seed is your backup to the account.