It should be simple, but I’m struggling with Custom Attributes. I understand how to add my own attribute like the page visited, but in the Webpushr example you mention Gender, User ID and E-mail.
I’ve added your sample code, but then the Custom Attribute will be Female, 874 and name@example.com 
How do I get those values from my own website – all users are logged in on Wordpress when they see the Webpushr, so basically I just want to take their registered E-mail and save that as a Custom Attribute ?