hi it will be in your hand book also the little credit card that you got with the car that holds all the information about the car will give you the number.
If it is a standard Vauxhall CD you enter the code in the following way.
For example, if the code is 3213. Press number 1 three times, number 2 twice, number 3 once and number 4 three times. You then need to press a confirm button, which depending on the model will be either FM, 5 or similar.