Open the Contacts app, then tap the Menu icon (at the upper-right corner of the screen).
Tap Speed dial.
Tap the speed dial number to assign.
Tap the Contact entry.
When you use the Menu icon (at the upper-right corner of the screen) to set a speed dial, the default number is automatically selected. If you choose the same entry for a speed dial again, the next saved number is automatically set for the speed dial.
The Speed dial icon in the contact entry allows you to set speed dials for selected phone numbers.
From the contact entry (either when creating it or while editing it later), tap the Speed dial icon to the right of the phone number you want to set with a speed dial.
Tap the speed dial number to assign to it.
Tap Save (at the bottom of the screen).