From the 'Calls' or 'Contacts' tab (at bottom of the screen), select and hold the phone number or contact. If selecting from the 'Contacts' tab, select the contact name then select and hold the appropriate number.
Select Add to Speed Dial (star icon on right side of the screen).
Remove a Speed Dial
From the home screen, select Phone.
From the 'Calls' tab (at bottom of the screen), select and hold the existing speed dial entry (at top of the screen).
Select Remove From Speed Dial (trashcan icon in lower right of the screen ).