Members Additonal Data Collection

I have another data collection with additional member information and i have the email linked as a reference to PrivateMembers data. I create a page under the member profile page and have a couple of user inputs going to the new data collection. How do i get the form or backend data collection, to automatically populate users email or user id information?

I have been through the url that shows you how to create your own member area but i am trying to use the default member area and just add an additional page