By scrolling a little, you will see the “Ringtone” field. Click on it, then on “Vibration”, and then on “Create a vibration.” iOS will then ask you to touch the screen in order to “create a vibration sequence.” It’s up to you to tap as you wish, then save your creation. Your contact will then vibrate uniquely when it calls you. Note that it is also possible to configure the vibration of SMS, or to reuse the same vibration as for calls.
Finally, if you want to use a personalized vibration for all your contacts and notifications, you can go to the menu Settings > Sounds and vibrations > Sounds and vibration sequences.