you need the 10 digit serial number from the box that the card is originally paired to, this can be found in the receivers services system info menu
you then take these 10 digits, and put them into a scientific calculator, and then press the hex button, if the result of this is LESS than 8 digits, add zeros to the START of the numbers to make it up to 8, this makes your boxkey that the receiver needs to know to be able to clear premium channels
whatever you do, DO NOT make public your receivers serial number or your boxkey, as these CAN be used to identify your account by sly/ND$
also, avoid the online boxkey generators, as ive never trusted these, and a LOT of people who have used them have had their cards / accounts disabled