It depends if you already dialed and hung up you need to tap your phone icon and then choose Recents from the bottom of the screen this will bring up a long list of calls, your keypad dialed number should be on the top of the list
To the far right of the number you will see an i with a circle around it tap in that and you will come to a Contact page with the number you dialed on it then choose Create New Contact
Sent from my iPhone 5
To the far right of the number you will see an i with a circle around it tap in that and you will come to a Contact page with the number you dialed on it then choose Create New Contact
Sent from my iPhone 5