When you are on a call, your in-call display will change to display additional in-call options:
If you wish to "Blind Transfer" a call, press the "transfer" button, and dial the number where you wish to send the call. The call will be sent, and hang up.
If you wish to do an "Attended Transfer," press the "att. transfer" button, and dial the number where you wish to send the call. Stay on the line, speak with the party, and hang up to send the call.
If the other party does not wish to take the call, they can hang up, and you will go back to your original phone call.