Being a total cretin when it comes to these sort of things could somebody please tell me how to do this.... I have the bulb just not the knowledge.

Much appreciated.

Yours is with the 2-bulb headlight, right?

Take a peek at the back of the headlight (HL) assembly. Pull-out the rubber glove, covering the base of the bulb fitting on the HL. Take a peek INTO the hole and look at how the metal-lock is placed, and then you'll understand.

If i'm not mistaken, you need to push back, then sideways. Or was it... (???) Sorry, dont remember. But it's really easy actually. The assembly is designed so that the contact points of the bulb, around the bulb would be the locking-plate for the assembly.

Careful to make sure that the circuit does not get shorted. The last time i changed that, i spent like a few blown fuses, wondering what the heck went wrong.