Same process as you did for your old one or check in Futaba site . I can tell you about JR/Spectrum but not sure about futaba, I think Futaba RX pairing is done as given below( Taken from Futaba 6EX manual page 9)
1. Place the transmitter and the receiver close to each other within one (1) meter
2. Turn on the transmitter.
3. Check the LED that is placed on the back side of the transmitter to see if the RF signal is active. When the green LED is ON
solid, the RF signal is being sent.
4. Turn on the receiver.
5. Press down the "ID SET" switch for more than one second, and release the switch. The receiver starts the linking operation.
6. When the linking is complete, the LED in the receiver will change to solid green. Please confirm that the servos will now
operate by your transmitter. Please refer to the table below for the LED status of the receiver's condition.
No signal reception Red : On
Receiving signals Green: On
Receiving signals, but ID is unmatched. Green: Blink
Unrecoverable failure (EEPROM, etc.) Red and Green
turn on alternately.
Replies
1. Place the transmitter and the receiver close to each other within one (1) meter
2. Turn on the transmitter.
3. Check the LED that is placed on the back side of the transmitter to see if the RF signal is active. When the green LED is ON
solid, the RF signal is being sent.
4. Turn on the receiver.
5. Press down the "ID SET" switch for more than one second, and release the switch. The receiver starts the linking operation.
6. When the linking is complete, the LED in the receiver will change to solid green. Please confirm that the servos will now
operate by your transmitter. Please refer to the table below for the LED status of the receiver's condition.
No signal reception Red : On
Receiving signals Green: On
Receiving signals, but ID is unmatched. Green: Blink
Unrecoverable failure (EEPROM, etc.) Red and Green
turn on alternately.
Good luck