Assuming it's a UK travelling iron it would have three wires and it would need a 13 amp 3-pin plug with a 3 amp or 5 amp fuse.
If the wires are brown, blue and yellow/green, connect the brown to the 'L' pin where the fuse is, the blue to the 'N' pin and the yellow/green to the 'E' pin, the thicker one. It's extremely important to make the connections correctly and not mix them up.
If the wires are a different colour, ask another question with the details.