TLDR: After entering your full name, you will be prompted to enter your date of birth either by selecting from a calendar or typing it in. Use the calendar to change year, month, and day as needed. After entering your date of birth, press the blue 'next' button to review your details.
Entering your Date of Birth
After entering your full name, you'll be asked to enter your date of birth. Depending on your phone, you may see a calendar to select your date of birth from, or boxes to type this into.
Once you have entered your date of birth, please press the blue 'next' button. You'll then have the option to review the details you have entered. You can read more about this stage here.