Now the sigma has two important accessories :

The magnet:

And the Sensor

Basically you need to fit the sensor on the lower part of the front fork. And the magnet on the wheel hub; Such that while the wheel spins, the magnet passes in front on the sensor. Ensure that the magnet is no further than 2mm from the sensor face while it passes. If you got a strong magnet, say one from a hard disk, you can afford to increase the gap.

Once installed, it looks like :

Note that the magnet is a different one. I lost the original. In fact had to stack three magnets to ensure that the gap is around 2mm. Wont be a problem if you can dig up a powerful magnet.

The sensor is connected to a mounting pad. Best thing is to fit the mounting pad onto the handle bar like this :

Another problem - the wire provided wont be long enough. You will need to cut it and insert wire in between in order to reach from the fork to the handle.

Yes - you will need a tube of quickfix with you. You can strap on the sensor using the thick rubber bands which come along with the package. But the magnet will need some hard glue to stick on the hub.

To test it, rotate the front wheel and check for activity on the sigma face.

Once all this is done, you are ready for stuff like this:

Good Luck...