Custom Fields are additional fields you can request in your sign up form to collect unique information about your users. Instead of asking for only the standard name and email, you can add fields for anything from phone, company name, city, to Twitter handle.To get started, go to the Admin Dashboard, click Settings Orders and accounts, and open Custom Sign Up Fields.
And that's it! You now have custom fields. To view the fields you have created, you can retrieve the data from user exports.