Hi @peter,
In the settings tab of the Create Account pop-up for the ServiceNow Account, in the Label field you can name your account however you wish.
In the Username field please type: admin.
In the Password field you need to provide the password you use to sign in to your developer instance (when you open the https://abc.service-now.com/ page in a browser). Please note this is different than the credentials used to sign in to the Developer Site.
In the Instance field you should type the name of your developer instance, which according to the example in your question is abc.
In the end, click on the Validate button so that you can make sure that the information entered is valid.
BR,
Dimitri