wot is the sequence or procedure to pair a key/fob for a peugeot 306?

the battery needed changing in my key but i am led to believe that i need to pair the key with the car, their is a certain sequence that you have to perform in order to do so, like press and hold a button for a few seconds then remove the key. can sum body please tell me the correct sequence. Peugeot 306 diesel V reg 1999.