Sometimes the cable that comes with the device just isn’t quite long enough. In most situations you can just make do, but what if you don’t want to? Making a short extension cord isn’t really difficult at all; all the parts shown below are available from any good hardware/electrical shop.
Wiring the plug is well-covered elsewhere on the web so I’ll only comment on wiring up the pins themselves: the easiest way is to insert the stripped wire all the way through until the insulation reaches the screw holding the wire down, and then snip off any remaining copper.
First you need to remove the socket cover.
Make sure that you take the cover and slide it all the way along the wire before you start wiring, otherwise you’ll find yourself wasting time taking it apart and putting it back together again.
Once the cover is off it’s simply a matter of wiring up the pins correctly – blue to neutral (labelled ‘N’), brown to live and green/yellow to the Earth.
Once that’s done simply slide the cover back along the wire and screw everything into place.