I made a post last week about adding an extension lead socket to a length of wire.
Now I'm going to detail the plug end.
So start by looking at the pins, here you'll find two screw holes that secure the male plug pin part to the back cover that you hold whilst plugging or unplugging.
Again, start by stripping your wire.
then cutting the phase wires slightly shorter than your earth wire, (so that if the cable is strained, your equipment would go dead before it became unearthed)
Now loosen the cable clamp and attach the wires to the plug terminals.
Finally clamp the cable in the cable clamp, push the back cover on, and screw it back into place with the screws that are next to the plugs inside the plug shroud.
Your extension lead is now complete.