Message and FaceTime use your Apple ID as the primary means of identification, so you don't necessarily need a phone number to use these services. However, if you do want to associate a phone number with your Apple ID for use with iMessage and FaceTime, you can do so by following these steps:
* Open the "Settings" app on your iPhone or iPad.
* Tap on your name at the top of the screen to access your Apple ID settings.
* Tap on "Name, Phone Numbers, Email".
* Under the "PHONE NUMBERS" section, tap "Add Phone Number".
* Enter your phone number and tap "Next".
* You will receive a verification code via SMS. Enter the code when prompted to complete the verification process.
Once your phone number is associated with your Apple ID, you can use it for iMessage and FaceTime. Keep in mind that if you want to use iMessage and FaceTime on multiple devices, you will need to associate the same phone number with each device.