Hi!
You’ll have to use the promptLogin() anyway in order to be able to get info about the user.
After ones login - You can use the currentUser method in order to retrieve some of the user’s data (check the links for more info).
In order to gain more data about your users you’ll have to make a form or use other platform to ask the users for their inputs (data like date of birth, country, phone number, etc.).
Whats make it easier is that one of the details you get about the user after the promptLogin is his _id .
Using this unique field you can add/show info directly to/from the item in the members collection that holds the specific users details.
Hope it helps!
Doron.