How to enable spdif

Maybe you should state your laptop's brand and model first. We can't read your mind.  

Your laptop manufacturer probably didn't want you messing around with that and disabled SPDIF in the hardware, especially if your laptop manufacturer goes by the name of Dell.

If it as a port it should be usable, I know Dell aren't that popular but in terms of functioning laptops, they're not that bad.

What OS are you using on your laptop and what have you tried? For vista and 7, the first place to start is control panel ->sound, and see what output options are available.

On Dell's old P4 based Inspiron 5150 laptops the SPDIF function was disabled in the hardware. Even if you plugged in Dell's adapter to their proprietary S-Video port the SPDIF port on the adapter wouldn't transmit any audio.