Can I install a 3.5mm adaptor in my mobile earphones ?

If the wires are the really thin type as mentioned above (e.g. they are coloured green, gold or red, with no apparent insulation, it means each strand is insulated) , you'll also need to burn back the insulation from the wires with a lighter. Otherwise the wire won't tin properly and be a nightmare to solder to the connector.

Umm...do you mean to say that the strands that are in the main wire are also insulated and are meant to be kept out of each other's contact ? And that you can't just twist the wires like the electrical copper wires ??