During the checkout process, customers will be required to enter their name, email, and password. You can choose to add up to three basic text fields to collect additional information from customers. You might want to know how they heard of you, what they're most excited to watch, etc. These text fields are a great way for you to learn about your audience through strategic questions that can help you understand what encouraged them to sign up.
Navigate to Settings > User Fields and add up to three custom text fields to appear on the signup page. Then Save your changes.
NOTE: Custom user fields cannot be mandatory. All custom user fields are optional.